Diabetes

A Complete Scientific Guide to Diabetes

Sheryl Huggins Salomon
By Medically Reviewed by 
Reviewed:
Medically Reviewed
Some people call it “the sugar” or “sugar diabetes,” but the correct term for the group of metabolic disorders that cause your blood glucose (sugar) level to be too high is diabetes mellitus, or diabetes for short.

It is not caused by eating too much sugar, per se, but it has everything to do with how your body handles the sugar you consume and what you do to manage the level of sugar in your blood.

More than 34.2 million adults in the United States — 10.5 percent of the population — had some form of diabetes in 2018.

It was the seventh leading cause of death in 2017.

Worldwide, more than 422 million people had diabetes in 2014.

Types and Prevalence of Diabetes Mellitus, Defined

A number of disorders are grouped under the umbrella of diabetes, usually identified by type. Each type is distinct in terms of what causes it, how it's treated, and the complications that can arise.

Here's a quick look at each type of diabetes: definitions, some fast facts, and how common each type is in the United States and worldwide.

Diabetes 101: What Are the Different Types of Diabetes?

Diabetes 101: What Are the Different Types of Diabetes?

Prediabetes and Insulin Resistance

Prediabetes is a condition that can lead to type 2 diabetes. To understand what causes it, you have to understand how the body handles glucose and processes it into energy.

Glucose enters the body primarily through the food and beverages you consume. The pancreas makes a hormone called insulin to help the glucose in your blood enter your muscles, fat, and liver and be used as energy. When the body does not use the insulin effectively, your pancreas initially produces more insulin to overcome this resistance. But when your pancreas is not able to keep up with the demand, the result is hyperglycemia, when blood glucose is too high.

Insulin resistance is the primary cause of prediabetes, but the causes of insulin resistance aren’t fully understood. Family history, advancing age, excess weight, and a sedentary lifestyle are among the known risk factors.

In 2018, 88 million adults had prediabetes in the United States, more than 1 in 3 people in the nation. It’s an age-related condition, experienced by nearly half of all adults older than 65.

A person with prediabetes has up to a 50 percent chance of developing diabetes within 10 years.

But it’s possible to get your blood glucose level back within a healthy range with lifestyle modifications such as eating a healthier diet; eating smaller, more frequent meals to keep your blood sugar stable; and exercising more, says Patricia Happel, DO, an associate professor and the associate medical director at the New York Institute of Technology College of Osteopathic Medicine in Old Westbury, New York. In fact, losing just 7 percent of your body weight (or 15 pounds if you weigh more than 200 pounds) may help lower your risk of developing type 2 diabetes by 58 percent.

Type 2 Diabetes 

Type 2 diabetes is caused by insulin resistance.

Between 90 and 95 percent of all diabetes cases are type 2, and nearly 1 in 5 people who have it don’t know they do.

The condition typically develops in people who are older than 45 and is more common in the United States among people who are Asian, Black, and Hispanic. It’s also strongly correlated with excess weight. About 89 percent of people with diabetes are overweight or have obesity.

 But the majority of people who are overweight do not develop type 2 diabetes. By their mid- to late seventies, about 2 in 10 overweight adults and 4 in 10 adults with obesity in the United States have been diagnosed with diabetes.

You can treat type 2 diabetes through diet and lifestyle changes to lower your blood glucose level and weight. In addition, many people with the condition monitor their blood glucose level regularly, take oral or injectable medications, and sometimes take insulin with a pen, pump, or needle.

If untreated or inadequately managed, type 2 diabetes may lead to numerous health complications, some of them life-threatening. They include periods of hypoglycemia (low blood sugar); diabetic neuropathy (nerve damage) that results in pain or numbness; foot and limb injuries, diabetic ulcers, deformities, or even amputations; kidney disorders; heart disease; blindness; skin problems; digestive disorders; sexual dysfunction; problems with teeth and gums; and problems regulating blood pressure.

Learn More About Type 2 Diabetes

Type 1 Diabetes

Type 1 diabetes is an autoimmune disorder in which a person’s own immune system attacks and destroys the beta cells in the pancreas that make insulin. Without that hormone, hyperglycemia develops. People who have type 1 diabetes must take insulin injections to replace the insulin their body doesn’t make, as well as monitor their blood glucose level daily.

Type 1 diabetes affects about 5 percent of the overall number of people with diabetes in the United States, with a higher prevalence among non-Hispanic white people than in other ethnic or racial groups.

This form of diabetes can occur at any age, but it usually appears in childhood or early adulthood, which is why health providers previously called it juvenile diabetes.

Unlike prediabetes, type 1 diabetes is a lifelong illness.

With careful management, a person who has it can live a normal life. Nonetheless, the average life expectancy of a person with type 1 diabetes is 12 years less than the general population, meaning you must stay on top of your treatment regimen if you have this type of diabetes.

It's also worth keeping an eye on advances in type 1 management technology, which may help improve longevity rates down the line.

Complications of type 1 diabetes are similar to those found in type 2 because in both cases, chronically elevated blood sugar causes long-term damage. But people with type 1 are especially vulnerable to developing a potentially life-threatening condition known as diabetic ketoacidosis (DKA). When the body doesn’t have enough insulin to convert glucose into energy, it begins to break down fat for fuel. The result is a buildup of acids in the bloodstream known as ketones.

“We typically tell patients that if your blood sugar is above 250 mg/dL [milligrams per deciliter], you want to test your urine for the presence of ketones — or check if you are going to exercise and your blood sugar is above 300 mg/dL. It can be life-threatening, because high levels of ketones in your blood can actually make your blood too acidic,” says Jordana Turkel, RD, CDCES, of Park Avenue Endocrinology and Nutrition in New York City.

One byproduct of DKA is fruity breath. Other symptoms include nausea, breathing problems, and loss of consciousness. If left untreated, DKA can result in kidney failure, fluid buildup in the brain, cardiac arrest, and even death. Hospitalization is often required to correct the condition with insulin, fluids, and other treatments. But you can prevent DKA with careful insulin management and monitoring of ketones in the urine — something you can do easily at home with an over-the-counter testing kit.

Learn More About Type 1 Diabetes

Gestational Diabetes 

To help ensure there’s enough glucose available to provide energy for a growing fetus, pregnant women normally develop a certain amount of insulin resistance. Most of them do not go on to develop gestational diabetes, but this condition does happen in up to 14 percent of all pregnancies in the United States.

Typically, treatment for gestational diabetes involves making diet and lifestyle changes, but sometimes, doctors prescribe oral diabetes medications or insulin to help control symptoms of gestational diabetes.

Gestational diabetes can lead to complications that affect the health of the mother, such as high blood pressure during pregnancy, called preeclampsia. Furthermore, the condition can cause babies to be born prematurely or to have a higher than normal birth weight, creating complications during delivery. The infants can go on to develop dangerously low blood sugar levels soon after birth. Later in life, they have an increased risk of developing obesity, heart disease, and type 2 diabetes.

Gestational diabetes usually goes away after the child is born, although half of all women with the condition will go on to develop type 2 diabetes.

Learn More About Gestational Diabetes

Type 1.5 Diabetes

This name is sometimes used to refer to latent autoimmune diabetes in adults (LADA). LADA involves progressive pancreatic beta cell failure similar to that seen in type 1 diabetes, but this is generally slower and occurs later in life.

“When you have a patient who is over the age of 30 and they come in with classic symptoms — the blood sugar is pretty high — if you give them metformin, they may be able to still manage some of their symptoms. But within the next five years, those beta cells that are producing the insulin are going to stop working, and then they are going to turn into a true type 1 patient requiring insulin,” says Turkel.

A correct LADA diagnosis is important so that effective treatments, such as the insulin therapy they will eventually need, aren’t delayed in favor of oral medications that are more appropriate to type 2 diabetes.

Generally, doctors diagnose LADA by testing for the presence of antibodies to pancreatic cells. A C-peptide test, a measure of insulin production, can also be helpful in making the diagnosis.

Type 3 Diabetes

Unlike the other types of diabetes mentioned, so-called "type 3 diabetes" is not an official diagnosis recognized by the medical community. Instead, it is a research term referring to evidence that Alzheimer’s disease and other neurodegenerative conditions are linked to insulin resistance in the brain.

Insulin affects metabolism in brain cells and the way brain cells signal the body for various functions. In addition, the hormone helps regulate blood flow to the brain and other parts of the body.

Research into type 3 diabetes looks at how various disruptions to the action of insulin may disrupt blood flow or create abnormal protein accumulations that lead to brain cell death and conditions such as cognitive impairment, dementia, Parkinson’s disease, and Alzheimer’s disease.

Learn More About Type 3 Diabetes

Signs and Symptoms of Diabetes

If you suspect that you have prediabetes or diabetes because of any of the symptoms below, you'll want to visit your healthcare provider immediately.

The symptoms are generally the same regardless of the type of diabetes mellitus in question. They are:

  • Increased thirst
  • Increased hunger (especially after eating)
  • Dry mouth
  • Frequent urination
  • Unexplained weight loss
  • Fatigue
  • Blurred vision
  • Numbness or tingling in the hands or feet
  • Sores or cuts that heal slowly or not at all
  • Dry and itchy skin (usually in the vaginal or groin area)
  • Frequent yeast infections

How Is Diabetes Diagnosed?

To be tested for prediabetes or any type of diabetes, you'll need to visit your healthcare provider's office. Unfortunately, you cannot test for the disease at home. As a first step in diagnosing you, the healthcare provider will take a medical history, including information about anyone else in your family who has had diabetes and what type. Next, they will likely order some of these lab tests to measure your blood glucose.

Fasting Plasma Glucose Test

This test is performed after you’ve had nothing to eat and no more than small sips of water for eight hours. Here’s what the results mean:

  • Normal is less than 100 mg/dL.
  • Prediabetes is 100 to 125 mg/dL.
  • Diabetes is 126 mg/dL or higher.

Hemoglobin A1C Test

This test shows how much glucose attaches to the hemoglobin in your red blood cells, on average, over the previous three months. You do not have to fast before taking it. Here’s what the results mean:

  • Normal is less than 5.7 percent.
  • Prediabetes is 5.7 to 6.4 percent.
  • Diabetes is 6.5 percent or higher.

Oral Glucose Tolerance Test (OGTT)

While there are multiple glucose challenges or tests, an OGTT is a common approach. For an OGTT, you’ll fast overnight and then have your blood drawn after you drink a glucose-containing liquid, and your blood will be tested one, two, and three hours later.

  • Normal is less than 140 mg/dL.
  • Prediabetes is 140 to 199 mg/dL.
  • Diabetes is 200 mg/dL or higher.

Random Plasma Glucose Test

This test for diabetes doesn’t require fasting beforehand, and while it can suggest diabetes with results of 200 mg/dL or higher, it is not typically used.

According to JDRF

and the National Institute of Diabetes and Digestive and Kidney Diseases,

other tests that may be administered include:
  • Autoantibody Tests These are most often done to test for type 1 diabetes or LADA. Common tests look for antibodies targeting insulin or certain pancreatic cells.
  • C-Peptide Test This measures a protein that mirrors the level of insulin in the body. Low levels can indicate type 1 diabetes or LADA.
  • Genetic Testing for Monogenic Forms of Diabetes Maturity-onset diabetes of the young and neonatal diabetes mellitus may be detected.

Causes and Risk Factors of Diabetes

You can take steps to lower your chance of developing types of diabetes that involve insulin resistance, such as prediabetes, type 2 diabetes, or gestational diabetes. (Type 1 diabetes isn’t known to be preventable.)

Diabetes Risk Factors You Can Help Control

Some of the strongest risk factors for developing insulin resistance are under your control:

  • Excess weight, especially a body mass index of 25 or higher for people in most ethnic groups in the United States; 23 or higher for Asian Americans; and 26 or higher for Pacific Islanders
  • A diet that is high in fat, added sugar, and refined carbohydrates
  • No regular exercise
  • Tobacco smoking
A healthy diet that is low in refined carbohydrates and a fitness routine are habits you can adopt to lessen the likelihood of developing insulin resistance.

Quitting smoking can help as well.

High blood pressure, a low level of HDL (“good”) cholesterol, a high level of triglycerides, and heart disease are also risk factors that may not be completely preventable, but you can help control them by making smart diet and lifestyle choices, as well as by taking medication as prescribed. You may not necessarily be able to prevent depression, another risk factor, but you can certainly be treated for it.

Diabetes Risk Factors You Can’t Control

Other risk factors are not in your control:

  • Age 45 or older
  • A family history of diabetes
  • Alaska Native, American Indian, Asian American, Black, Hispanic or Latino, Native Hawaiian, or Pacific Islander ethnicity
  • A history of gestational diabetes or a child with a birth weight of 9 pounds or more
  • Polycystic ovary syndrome (PCOS)

People should know that they can do things to lower their risk of developing the insulin-resistant forms of diabetes, but they should not feel guilty if they develop the disease anyway, says Joshua D. Miller, MD, the medical director of diabetes care at Stony Brook Medicine in New York, who manages type 1 diabetes himself.

“No one wakes up and says they want to develop diabetes, whether it be type 1 or type 2. Developing diabetes is completely out of most people’s control — even along the type 2 diabetes spectrum where lifestyle and obesity play a larger role in developing the disease,” Dr. Miller says. “Working past the notion that you’ve done something wrong because your blood sugar is too high is probably the most important challenge to overcome in order to help people become better at managing their disease.”

Is Diabetes Hereditary? The Role of Genetics in Risk

Diabetes does tend to run in families, and researchers have identified genes associated with various types of the disease. Forms of diabetes can be either monogenic, meaning you can pinpoint and test for a single gene, or polygenic, meaning it involves multiple genes and a complex interaction with lifestyle and environmental risk factors.

Polygenic Diabetes

Type 1, type 2, and gestational diabetes are all polygenic diseases.

While you can’t pinpoint a single gene mutation that causes them, there’s a growing field of testing called polygenic risk scoring. Polygenic risk scoring looks at common genetic variations known as single nucleotide polymorphisms that are associated with your risk of developing diabetes.

While your risk score won’t predict with 100 percent certainty whether you’ll develop a polygenic form of diabetes, it may help you focus on taking preventive measures, says Mónica Alvarado, a certified and licensed genetic counselor and the regional administrator for genetic services at Kaiser Permanente in Pasadena, California. “The advantage of that is that someone might be more motivated to control their diet and exercise, and to monitor their glucose and hemoglobin A1C more regularly, than if they just have information that their risk for diabetes is higher than that of the average person,” she says.

Alvarado also says that the influence of family history is complex, and it’s hard to know whether relatives are sharing genetic variations alone or also sharing a diet, lifestyle, and environment that make them more prone to developing diabetes.

In the case of gestational diabetes, many women who develop the condition have at least one close family member, such as a parent or sibling, who also had the condition or type 2 diabetes.

Monogenic Diabetes

Between 1 and 4 percent of all diabetes cases are monogenic. Two of the most common forms are maturity-onset diabetes of the young (MODY), which usually appears in teens and young adults; and neonatal diabetes mellitus (NDM), which is most common in newborns and infants.

Some forms of MODY result in slightly high levels of blood sugar that remain stable throughout life, with no symptoms or mild symptoms and no complications. Other forms may require treatment with insulin or a class of oral medications called sulfonylureas, which increase the release of insulin from beta cells.

The most common mutations for MODY are found in the GCK gene or the HNF1A gene.

Infants with NDM do not produce enough insulin. The condition is often mistaken for type 1 diabetes. Babies with NDM tend to be born undersize and grow less rapidly than peers without the disorder. About half of babies with NDM will have it for life; for the other half, it will disappear, but it can reappear later. Most testing for NDM looks at three genes: KCNJ11, ABCC8, or INS.

Learn More About Whether Diabetes Is Genetic

Treatment and Medication Options for Diabetes

If you’ve been diagnosed with diabetes, your treatment regimen will vary based on your individual health and the type of diabetes you’re managing. But one treatment that's often closely linked with the condition is insulin.

Insulin

Insulin therapy is typically self-administered by injection, up to several times a day, using a needle, syringe, pen, or pump.

There are a few types of insulin to get you through the day.

Basal, or Long-Acting, Insulin This form begins to work several hours after injection and keeps working steadily over a 24-hour period without any peak effect. It's always in the background regardless of what or when you eat. “It’s what the pancreas would be dripping into the system constantly,” says Grace Derocha, RD, CDCES, of Blue Cross Blue Shield of Michigan in Detroit. Examples include levemir (Detemir), degludec (Tresiba), and glargine (Lantus, Toujeo, and Basaglar).

Intermediate-Acting Insulin Isophane (Humulin N), Novolin N, and lente (Lente) are slowly released into the bloodstream so they can last up to 24 hours. If someone is on a pump, the amount is adjusted slightly depending on the level of activity or whether someone is awake or asleep, says Derocha.

Bolus, or Mealtime, Insulin This type refers to the amount of insulin that is given to cover the glucose that comes through food. The amount of bolus insulin you need depends on the size of the meal you’ve just eaten. Fast-acting insulins such as insulin aspart (NovoLog), insulin glulisine (Apidra), and insulin lispro (Humalog), which are taken before a meal, work within 15 to 30 minutes and last for several hours.

Learn More About Insulin

Oral Medications

Instead of or in addition to insulin, a number of oral medications are used to treat diabetes, particularly in people whose bodies still make some insulin and whose A1C is below 9.

Metformin Including brand names Glucophage XR, Fortamet, Glumetza, this is generally the first line of treatment for type 2 diabetes and is sometimes used to treat prediabetes and gestational diabetes as well. It belongs to the biguanide class of drugs and helps control blood sugar by lowering the release of glucose from the liver and improving insulin resistance.

Long-term use is associated with vitamin B12 deficiency, so periodic screening of B12 levels is recommended.

Other oral medications for diabetes include:

Sulfonylureas Glipizide (Glucotrol), glimepiride (Amaryl), and glyburide (Micronase) belong to this class of drugs, which stimulate the pancreas to release more insulin when taken with meals.

Meglitinides Repaglinide (Prandin) is a meglitinide, which also stimulates the pancreas to release more insulin when taken with meals.

Thiazolidinediones The only approved drug in this class is pioglitazone (Actos), which makes the body more sensitive to the effects of insulin.

DPP-4 Inhibitors Sitagliptin (Januvia), linagliptin (Tradjenta), saxagliptin (Ongliza), and aloglipitin belong to this class. These drugs improve the level of insulin made after a meal and help lower the amount of glucose made by the body.

GLP-1 Receptor Agonists Liraglutide (Victoza), dulaglutide (Trulicity), and Ozempic (semaglutide) belong to this class of drugs, which mimic the effects of the incretin hormone GLP-1, which is excreted during a meal and lowers blood sugar.

GLP-1 Receptor and GIP Agonists There is currently one drug available in this class, tirzepatide (Mounjaro), which the U.S. Food and Drug Administration approved in May 2022. Studies suggest tirzepatide helps lower A1C and manage hunger, in some cases leading to significant weight loss.

SGLT2 Inhibitors Canagliflozin (Invokana), dapagliflozin (Farxiga), and empagliflozin (Jardiance) belongs to this class of drugs, which prompt the kidneys to get rid of more glucose through urine.

Glucose Monitoring

Among the most powerful tools to manage diabetes or prediabetes is glucose monitoring. It can be done at home using a glucose monitor or meter, which analyzes a drop of your blood that you draw by pricking your finger with a lancet and then placing the blood drop on a disposable test strip that is inserted into the meter. You should consult with your doctor to set blood glucose level goals, but keep in mind that blood glucose for an adult without diabetes is below 100 mg/dL before meals and fasting, and less than 140 mg/dL two hours after meals (called postprandial glucose).

There are also continuous glucose monitors that you wear on your arm or abdomen for 10 to 14 days, including Freestlye Libre, Dexcom G6, and Medtronic Guardian.

Diet and Lifestyle Tips to Help Keep Blood Sugar in Check

Depending on the type of diabetes you're managing, you'll need to work with your healthcare team to devise a diet and lifestyle program that meets your individual needs. Then you'll need to build a support team in and outside of the home to help you stay on track.

Focus on Quality Food

As with any healthy diet and lifestyle, you'll want to focus on eating whole, fresh foods that are rich in fiber and on limiting your intake of processed food that is high in salt, sugar, saturated fat, and unhealthy trans fat. You’ll likely have to cut down on the amount of carbohydrates (particularly sugars and starches) you consume, especially in the form of beverages with added sugar, such as juice, soda, and sports or energy drinks.

Nonetheless, with proper balance and smaller portions, carbohydrates — which also include dietary fiber — can and should remain a part of your diet.

Become a Carb-Counting Pro

“We try to teach carb control, carb consistency, and carb counting,” says Derocha. “I call it the ‘three carbohydrate C's’ that are important for any type of diabetes and blood sugar control.” In short: Counting your carbohydrates and keeping them at a consistent level for every meal can help you to stabilize and control your blood sugar.

Ultimately, you’ll need to consult your primary-care doctor or registered dietitian to find out how many carbs you should be eating per day, as they’ll take any insulin or medication you’re on into account. But for now, the recommended carbohydrate intake for most people with diabetes is about 50 percent of total calories consumed.

Consider Glycemic Index and Glycemic Load

Some people also look at how various foods containing carbohydrates are likely to raise their blood sugar, according to the food's rank on the glycemic index (GI) and its glycemic load (GL).

The GI is a measure of how food raises blood glucose levels. Foods are ranked on a scale of 0 to 100, with 100 being pure glucose. Low-GI foods rank at 55 or less (such as oatmeal, sweet potatoes, and most fruit); medium-GI foods rank 56 to 69 (brown rice and corn); and high-GI foods (think bagels, popcorn, and melon) rank 70 and above.

“A high-glycemic-index food will raise blood sugar more than a food on the medium or low end of the spectrum,” explains Derocha, noting that “the glycemic load itself is really a better way to tell you how that particular food will then affect your blood sugar.” This is because GL compares the ability of the same amount of carbs in each food to raise your blood sugar higher.

To figure out a food’s glycemic load, multiply its GI by the number of carbohydrate grams in a serving, then divide that by 100.

Low-GL foods rank from 1 to 10; medium-GL foods rank from 11 to 19; and high-GL foods rank 20 or higher. So while 1 cup of watermelon has a high GI, of 76, it has a low GL, of 8.

Knowing a food’s specific GL can help you lower and control your blood sugar, but Derocha stresses that it’s most effective to use this strategy in concert with carb counting and healthy eating.

Explore the Ketogenic Diet and Diabetes

Some people with type 2 diabetes go on a ketogenic, or keto, diet diet; this high-fat, low-carb regimen forces your body to burn fat instead of carbs for fuel. Because the approach is so low in carbohydrates, the body quickly depletes its store of glucose and then enters a natural state of ketosis, in which fat is broken down by the liver into acids known as ketones, which become the main source of fuel. “For type 2 patients on medication or who have PCOS with insulin resistance, a version of the ketogenic diet can help,” says Turkel, particularly if losing weight is a goal.

But, she adds, people who have insulin resistance are typically trying to manage a lot of diet and lifestyle changes at once to help control their blood sugar, so she doesn’t recommend the rigors of a ketogenic diet as a long-term solution. Additionally, if you are taking oral diabetes medications, you may be at risk of potentially serious complications, like hypoglycemia.

Eat a Diabetes-Friendly Diet When Managing Gestational Diabetes

“The first line of treatment is diet and exercise, and then steadily monitoring their blood sugar,” says Derocha. “We usually have people check their blood sugar anywhere from four to six times a day when they have gestational diabetes.” If that is not enough, insulin is the preferred course of treatment rather than oral medications.

Based on her personal experience with gestational diabetes, Derocha says that it’s manageable. “During my pregnancies, I did not have to take any medication, and I did not take any insulin, because I was able to control it with my diet and lifestyle changes,” she says.

Don't Discount the Importance of Exercise

The vital role that exercise plays in blood sugar management cannot be overstated.

“When we are exercising, we automatically use sugar, or blood glucose, as our first form of energy,” Derocha says, explaining that as blood glucose is depleted, “your body will then take some of the glycogen stores, which is excess blood sugar stored in your cells, to then use as energy.” Furthermore, Derocha adds, “When we have more lean muscle mass, we are less insulin resistant.”

As for what you should do for exercise, Dr. Happel suggests finding an activity you like and sticking with it. “Make it fun, make it something you enjoy doing,” she says. “Do it with family, do it at work. If you like to dance, then dance. Walking, working in the garden — just be active.”

Keep frequency in mind, too. The U.S. Department of Health and Human Services recommends 30 minutes of moderate to vigorous exercise at least five days per week, but be sure to talk to your healthcare team before you begin exercising so they can advise you on the best way to proceed.

Particularly if you have nerve damage in your feet or legs caused by diabetes, you may have to make some accommodations to exercise safely. “People with diabetes, especially if they have neuropathy [nerve damage] or are at risk for it, should go to the podiatrist, especially if they are older or unable to get to their toes and feet,” says Derocha. You may need to get special shoes or compression socks for exercise. Also, be sure to keep your feet and toenails clean, and inspect them before and after exercise for any wounds or breaks in the skin.

Complications of Diabetes

Poorly managed blood sugar can lead to serious and even life-threatening health complications, regardless of the type of diabetes you have. But there are some specific health risks by type that you should be aware of.

Prediabetes

The main complication of prediabetes is that insulin resistance can develop into type 2 diabetes if it remains unaddressed. The good news is that you still have time to reverse this condition by eating a healthier diet and exercising — and if you are overweight, losing even a moderate amount of weight.

Miller tells patients that no matter how much weight they need to lose to get to an ideal body weight, “if you lose 5 pounds, or 10 pounds even, your numbers will dramatically improve.”
Additionally, one can develop prediabetic peripheral neuropathy, a form of nerve damage that is a precursor to the far more common diabetic peripheral neuropathy. The excess glucose in the blood slows down or alters the conductive properties of the nerves until the electrical impulses to the nerves don't function properly. Numbness, tingling, and burning sensations can result, especially in the feet and hands.

Type 1 and Type 2 Diabetes

A number of complications can arise from types 1 and 2 diabetes if they’re uncontrolled or poorly controlled for a long period of time:

  • Damage to blood vessels, resulting in heart disease, stroke, and kidney disease

  • Blindness, including diabetic retinopathy, diabetic macular edema, cataracts, and glaucoma caused by swelling, nerve damage, or damage to the tiny blood vessels in the eye

  • Bladder problems and sexual dysfunction, also due to damage to blood vessels or nerves

  • Orthostatic hypotension, a drop in blood pressure upon standing up caused by nerve damage

  • Slow-healing wounds, as a result of blood vessel damage

  • Diabetic ketoacidosis, a buildup of acids in the bloodstream known as ketones, occurring when the body doesn’t have enough glucose to use as fuel.

Other Possible Complications of Diabetes

Numerous complications are associated with diabetes mellitus.

Diabetic Neuropathy Nerve damage affects nearly 60 percent of people with diabetes. Distal symmetric polyneuropathy is the most prevalent within that group. With this form of neuropathy, the most distant nerve fibers from the central nervous system malfunction first. “It usually starts in the feet. [You’ll] feel tingling or numbness at the bottom of the feet, and then [it] may slowly progress upward in the foot to the ankle and the legs,” says Happel.

The pattern is usually symmetrical, affecting limbs on both sides. Sometimes a burning sensation takes hold, which Happel says is sometimes mistaken by patients for athlete’s foot. Eventually, numbness and then profound loss of sensation can set in, along with the loss of reflexes.

With the pain gone, people may think they’re getting better, but actually this is bad news. They become injury prone, without the signal of pain to tell them when they have sustained an injury and need treatment. This can lead to further complications, such as ulcers, sores, and the need for limb amputations.

The first line of treatment for diabetic neuropathy is to get blood sugar under control to help prevent further nerve damage. After that, over-the-counter and prescription medication may be prescribed for the pain and, in some cases, electric nerve stimulation.

Amputations Unfortunately, complications from neuropathy, as well slow wound healing, can lead to ulcers, gangrene (a potentially life-threatening condition caused by the death of wounded tissue), and bone infections so severe they require amputation. In the United States, more than 108,000 people with diabetes were discharged from the hospital in 2014 after having a lower-extremity amputation.

If gangrene is caught in time, doctors can treat the condition with antibiotics, surgery, and oxygen therapy.

Likewise, a bone infection can be addressed with antibiotics and surgery.

But the best treatment is prevention. Inspect your feet and any other areas where you have problems with your skin or nerve damage on a daily basis. Get any cracks, abrasions, or wounds addressed right away by a medical professional, even if they don’t hurt.

Charcot Neuropathic Osteoarthropathy Called Charcot for short, this motor neuropathy results when joints in the feet are unable to respond properly to the force being put on them because of nerve signal disruption. Lack of coordination leads to injuries, and the resulting inflammation can create microfractures that multiply over time and destroy the structural integrity of feet and limbs. People with Charcot end up with foot deformities and ankle dislocations. Treatment focuses on stabilizing the affected area (with a cast, for instance), keeping too much weight off it, and reducing the swelling.

Hypoglycemia It may sound counterintuitive, but diabetes can lead to sudden drops in blood sugar known as hypoglycemia. These drops can happen when the insulin or another diabetes medication isn’t at the right dosage for what you’re eating or your level of activity. It can also be caused by a missed meal or one that doesn’t have enough carbohydrates in it.

Symptoms of hypoglycemia include jitteriness or shakiness, blurred vision, fatigue, dizziness, disorientation, a fast or irregular heartbeat, irritability, weakness, or extreme hunger. Severely low blood sugar may result in unconsciousness and seizures.

Be sure to check your blood glucose if you experience any of these symptoms, and if your number is below 70 mg/dL (or your agreed-upon target level), ingest 15 grams of carbohydrates right away in the form of glucose pills, glucose gel, soda, regular fruit juice (except for orange juice if you have kidney disease, because of the drink’s compromising potassium level, which can strain the kidneys), raisins, hard candies, or a tablespoon of honey or sugar. If people cannot act for themselves, someone else may have to give them a glucagon injection, which the person should carry in case of emergencies. Glucagon is a hormone that causes the liver to break down glycogen into glucose.

The best way to avoid hypoglycemia is to check your blood glucose level regularly, eat meals with your recommended amount of carbohydrates at regular intervals, and be mindful of any adjustments you may need to make in what you eat or how much insulin you take when you exercise.

Hyperglycemic Hyperosmolar Nonketotic Syndrome When your blood glucose becomes extremely high, particularly over 600 mg/dL, a life-threatening condition known as hyperglycemic hyperosmolar nonketotic syndrome (HHNS) can occur.

The body will try to excrete the extra blood glucose in the urine, leading to severe dehydration and an imbalance of electrolytes. The result can be brain swelling, abnormal heart rhythms, seizures, coma, organ failure, or even death.

Happel says that one reason why people end up with HHNS is noncompliance with their insulin treatment regimen, especially among teens and college students with type 1 diabetes. “They don’t want to be different from their friends, so they don’t take their insulin. Then they go out and have some drinks. Alcohol, when it is broken down in the body, is also broken down into sugars. But they are not taking their insulin, and they wind up in the hospital,” Happel explains.

But people with any type of diabetes are at risk for this complication, especially if they’re insulin-dependent. Noncompliance isn’t the only trigger, either; sometimes a person who develops HHNS is fighting another illness that has weakened and dehydrated them, says Happel.

Treatment generally happens in the ICU. “One of the first things is fluid resuscitation. They are 4 to 6 liters of fluid behind by the time they develop these complications,” says Happel. Insulin is administered, and electrolyte balances are also addressed. The best way to avoid HHNS is to monitor your blood sugar, take any insulin or medications you are prescribed in the proper dosage, and stick to your diet and exercise plan to manage diabetes.

Gestational Diabetes Complications

Preeclampsia is a common complication of gestational diabetes, possibly leading to the need for an early delivery. Full-term babies born to mothers with gestational diabetes can weigh 9 pounds or more, which can create complications during delivery and increase the likelihood that a cesarean section is needed.

Once they are born, the infants are also more likely to develop dangerously low blood sugar, jaundice, or problems breathing. Later in life, these children have an increased risk of developing obesity and heart disease. Both mother and child have an increased risk of developing type 2 diabetes. Diet and lifestyle modifications are most often recommended to keep gestational diabetes under control and minimize the chance of complications.

Is It Possible to Reverse Diabetes? Answers to FAQs Like This

Short answer: Maybe. Get more details on that common question and others below.

Q: How do I know if I have diabetes?

A: Common symptoms of diabetes include excessive thirst, a constant feeling of hunger (especially after eating), and frequent urination. If you are experiencing these symptoms — especially if you have a family history of diabetes — visit your doctor. They will examine you, take note of your health history, and run tests of your blood glucose level to possibly arrive at a diagnosis. If you have a fasting plasma glucose of 126 mg/dL or higher, or an A1C of 6.5 or higher, you have diabetes.

Q: Does sugar cause diabetes?

A: Not really, but diabetes has everything to do with how your body handles the sugar you consume. Diabetes mellitus is a group of metabolic disorders that cause the level of glucose (sugar) in your blood to be too high. This is called hyperglycemia.

If you’re diagnosed with a type of diabetes, you will likely have to cut down on the amount of carbohydrates (particularly sugars and starches) that you eat and drink, specifically in the form of beverages with added sugar. To keep your blood glucose level stable, you may need to count the carbohydrates you consume, take insulin or oral medication, and monitor your blood glucose. With proper balance and smaller portions, sugar and other carbohydrates can and should remain a part of your diet.

Q: Which is worse: type 1 diabetes or type 2 diabetes?

A: Both are conditions with life-altering symptoms and complications, but they have very different causes. Type 2 diabetes is caused by insulin resistance, when the body stops responding well to insulin and the blood glucose level rises too high.

It’s typically diagnosed in people older than 45. Whether you develop the disease depends on a combination of risk factors under your control (including diet, exercise, and lifestyle), as well as those you can’t control (such as genes, family history, age, and ethnicity). Even if you have one or more risk factors, it’s possible to reduce your risk of developing type 2 diabetes by sticking to a healthy diet and lifestyle.

But type 1 diabetes is the result of an autoimmune disorder in which a person’s own immune system attacks and destroys the insulin-making cells in the pancreas. Without that hormone, the blood glucose level rises too high and insulin injections must be taken daily to replace the insulin that the body doesn’t make.

It typically appears in teenagers and young adults, and researchers don’t believe it’s preventable. “Autoimmunity in type 1 diabetes is unavoidable for those who get it,” says Miller.

Q: Is type 2 diabetes genetic? What about type 1 diabetes?

A: Both type 1 and type 2 diabetes are polygenic, meaning they involve multiple genes, and their development is affected by lifestyle and environmental risk factors.

A fledgling field, called polygenic risk scoring, looks at common genetic variations known as single nucleotide polymorphisms that may be associated with your risk of developing type 1 or type 2 diabetes.

Nonetheless, risk scoring cannot tell you with certainty if you will develop one of the disorders. Family history is another risk factor, but it’s hard to know whether that is due to sharing genetic variations with relatives or to also having a diet, lifestyle, and environment in common.

Q: What does prediabetic mean?

A: If you have prediabetes, it means your body has stopped responding well to the hormone insulin — a condition known as insulin resistance — and your blood sugar is higher than normal, though not high enough to qualify as diabetes. If you don’t reverse the trend through changes in diet, exercise, and lifestyle, you may eventually develop type 2 diabetes.

Family history, advancing age, excess weight, and a sedentary lifestyle are among the known risk factors for developing insulin resistance.

One way to know if you have prediabetes is to take a hemoglobin A1C test, which measures how much glucose attaches to the hemoglobin in your red blood cells, on average, over the previous three months. A normal A1C result is below 5.7 percent. If your A1C is 5.7 to 6.4 percent, then you have prediabetes. At 6.5 percent or above, you have diabetes.

Q: Can people with diabetes donate blood?

A: Yes, it is possible to donate blood, with a few caveats. “I want them to have their blood sugar under really good control,” says Derocha. Not only is that important for the health of the individual — since donating blood (along with the glucose it contains) removes a small amount of fuel from your system — but it is a requirement of the American Red Cross.

Taking oral medications and most forms of insulin to maintain that control is okay, but if you have ever used bovine (beef) insulin made from cattle from the United Kingdom since 1980, you are ineligible, because of a concern about Creutzfeldt-Jakob disease, also known as “mad cow disease.” If you're in doubt about your blood sugar level or what insulin you have taken, check with your doctor.

Q: Can people with diabetes eat fruit?

A: If you have diabetes, you absolutely can eat fruit in moderation and paired with other types of nutrients. First, look for fruit options lower on the glycemic index, says Turkel. The GI is a measure of how food raises blood glucose levels. Foods are ranked on a scale of 0 to 100, with 100 being the GI of pure glucose. Most fruit is low on the GI, at 55 or below. Looking at the glycemic load, a related measure that compares how the same amount of carbohydrates in each food will raise your blood sugar, gives an even better picture of how fruit or any other food with carbohydrates will affect your blood sugar.

“At one given time you don’t want to have more than 1 cup of cut fruit or a cup of berries or one small piece of fruit,” Turkel advises. “And you never want to eat a piece of fruit or cup of fruit without a protein or a fat.” Adding protein or fat slows down the impact of the fruit’s sugar in your bloodstream and lessens the chance of a spike in blood sugar. “If you like fruit, pair it with some protein — a handful of nuts, a hard-boiled egg — and be strategic about it. And limit it to only twice a day.”

Q: What is a diabetic diet?

A: If you’re diagnosed with diabetes, you may receive a meal plan that involves keeping track of the amount of carbohydrates (which include sugars, starches, and fiber) in your food and drinks. You will be encouraged to count carbohydrates and keep them at a consistent level for each meal you eat to help stabilize your blood sugar. Your healthcare team can help you decide how many carbs it’s safe for you to take in each day. They’ll take any medication or insulin you’re on into account. But it’s good to know that the recommended amount of carbohydrates for most people with diabetes is about 50 percent of total calories consumed.

Q: What foods should people with diabetes avoid? 

A: There are very few foods that a person with diabetes ought to totally avoid. If you practice portion control, count your carbohydrates, and eat a healthy balance of nutrients, you should be able to continue eating many of the foods that you like in moderation. “I don’t believe in taking away foods from patients. Instead, I believe in educating them in how to appropriately eat the foods,” Turkel says, adding, “if they are drinking juice and regular soda, and sweetened beverages like that, that is one thing that I do recommend they cut out. That’s an easy fix.” You’ll also want to limit your intake of processed food that is high in salt, sugar, and saturated and trans fat.

Q: Can people with diabetes get tattoos?

A: Yes, but you should check with your doctor first, and be sure of a few things, says Derocha: “Obviously you would not do this if you were pregnant [and have gestational diabetes], but with type 1 or type 2, you’d really have to have good blood sugar control. That is because one of the side effects of poor sugar control is an inability to heal [well] and to fight off infection.”

She also cautions against having tattoos if you have kidney problems or diabetic peripheral neuropathy (nerve damage), particularly in the regions where you want to place the tattoos. Again, this is to guard against the possibility of an infection that will sicken you or heal poorly.

Q: What is diabetes insipidus?

A: This condition is unrelated to type 1 or type 2 diabetes. Instead, it’s caused by an inability of the kidneys to balance fluid in the body.

As a result, the body excretes large amounts of urine. In this condition, blood glucose levels remain normal.
“It presents as excessive urination and extreme thirst, similar to diabetes mellitus, but it’s actually a result of inadequate output of a [pituitary-released] hormone called antidiuretic hormone,” says Turkel. Also known as vasopressin, the hormone controls the kidneys’ fluid removal rate through urination.

Q: What does diabetic nerve pain feel like?

A: Diabetic peripheral neuropathy, or nerve damage, can develop when elevated blood sugar damages nerves, which then send sensory signals to the central nervous system in an altered and disordered fashion. The result can be neuropathic pain that is burning or tingling in nature.

After the condition is diagnosed and blood sugar is brought under control to prevent further nerve damage, your healthcare provider may prescribe over-the-counter or prescription medication for the pain. In rare cases, you may undergo electric nerve stimulation to alleviate symptoms.

Q: Can dogs get diabetes?

A: Yes, they can. Like us, they can develop insulin deficiency diabetes (which is like type 1 diabetes in humans) and insulin resistance diabetes (which is like type 2 in people). The insulin-deficient type is most prevalent in canines, though older, obese dogs in particular can develop insulin resistance. The symptoms and treatments of diabetes in dogs are not unlike what humans experience. Breeds that may be at a higher risk for the condition include miniature poodles, bichons frisés, Australian terriers, fox terriers, cairn terriers, pugs, dachshunds, miniature schnauzers, pulis, Samoyeds, keeshonden, and beagles.

Q: Can you die of diabetes?

A: Yes. Diabetes was the seventh leading cause of death in the United States in 2017, claiming nearly 84,000 people, for whom it was the underlying cause of death listed on their death certificate.

People with type 1 diabetes have an average life expectancy of 68.6 years, which is 12.2 years less than the average life expectancy overall, one study suggests.

In both type 1 and type 2 diabetes, the long-term damage caused by elevated blood sugar can lead to heart disease, stroke, kidney disease, nerve damage, and other life-shortening complications.

Q: Can diabetes cause low blood sugar?

A: Yes, having diabetes can lead to sudden drops in blood sugar, also called hypoglycemia. These drops can occur when your insulin or medication dosages don’t align with your eating and exercise habits. Hypoglycemia can also be caused by missing a meal or not having enough carbohydrates in a meal.

Signs that your blood sugar has dropped can include feeling shaky or jittery; having blurred vision, fatigue, dizziness, disorientation, or fast or irregular heartbeat; being irritable; and feeling weak or extremely hungry. If left untreated, hypoglycemia can result in unconsciousness and seizures.

If you have diabetes, check your blood glucose if you notice any of these symptoms, and if your number drops below 70 mg/dL (or the target you’ve set with your doctor), take in 15 grams of carbohydrates right away, then check your blood glucose 15 minutes later. Repeat this until your blood glucose is on target. This is called the rule of 15s. If it doesn’t help you meet your target after several attempts, use oral glucose.

The best way to avoid hypoglycemia is to check your blood glucose regularly, eat regular meals with the right amount of carbohydrates in them, and note any adjustments you might need to make in what you eat or how much insulin you take when you exercise.

Q: Can diabetes be reversed?

A: Insulin resistance (which is seen in type 2 diabetes and gestational diabetes) is much easier to reverse in the prediabetes stage, says Happel. Lifestyle changes can help you to get your blood glucose back within normal range: a healthier diet; smaller, more frequent meals to keep your blood glucose stable; regular exercise; and weight loss.

Once you have developed type 2 diabetes, it’s much harder to get your blood sugar back into normal range, though you can certainly lower it with diet, lifestyle modifications, and medication, says Happel. “When they get to the point where they need insulin, it’s harder to reverse, but it can be.” Bariatric surgery (weight loss surgery) has helped some obese people with type 2 diabetes regain normal blood sugar levels and stop taking diabetes medication.

Yet once your A1C passes 8, you’re less likely to be able to reverse the condition, Happel says. “What is happening is that your pancreas is starting to burn out,” she explains, after which you will definitely need insulin for the foreseeable future.

For those who have had gestational diabetes, the insulin resistance usually reverses after the child is born, but notably, half of all women with the condition during pregnancy will go on to develop type 2 diabetes later in life.

Currently, there’s no practical way to get rid of type 1 diabetes or cure it. Thus, for now, these individuals must take insulin for life. A limited number of people have undergone transplantation of pancreatic islets (cell clusters that include the insulin-producing beta cells) from a deceased donor, but scientists consider this an experimental procedure, with the same risks and expenses that are associated with organ donation.

At this point in time it is “not realistic, not very effective,” comments Miller, who is nonetheless hopeful that research into beta cell regeneration and transplantation will bear fruit in the future.

Additional reporting by Moira Lawler.

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