Type 2 Diabetes

Type 2 Diabetes

How Is Type 2 Diabetes Diagnosed?

Sheryl Huggins Salomon
By Medically Reviewed by 
Reviewed:
Medically Reviewed
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An A1C blood test is sometimes used to screen for diabetes.iStock
Is there a diabetes diagnosis in your future? Each year more than 1.5 million people in the United States receive one.

More than 9 in 10 people with diabetes have type 2, which occurs when the body does not use insulin properly, and your blood sugar (glucose) level rises too high.

Most of the rest have type 1 diabetes, an autoimmune disease in which beta cells, the insulin-producing cells of the pancreas, are damaged, and little or no insulin is made to process glucose.

Should You Get Screened for Type 2 Diabetes?

If someone in your family has had type 2 diabetes, your chances of developing it rise. “Patients with a first-degree relative — mother, father, sibling — with type 2 diabetes have a two to threefold risk of developing it,” says Sarah Rettinger, MD, an endocrinologist at Providence Saint John’s Health in Santa Monica, California.

Other risk factors for type 2 diabetes include:

  • Age — older than 45
  • Being overweight
  • Race or ethnicity: Black, Hispanic, Native American, Asian American, or Pacific Islander
  • Inactivity
  • Smoking
  • History of gestational diabetes, which happens during pregnancy
One or more of the common symptoms of diabetes can also indicate that a diagnosis is in your future, if you act on the warning signs. Symptoms include:

  • Excessive thirst
  • Excessive urination
  • Eating more than usual
  • Unexplained weight loss
  • Fatigue despite sleeping an amount of time you would consider to be restful
  • Blurred vision
  • Swollen or red gums
  • Dry mouth
  • Tingling, burning, or numbness in your hands or feet
  • Confusion
  • Irritability
  • Wounds that heal slowly or not at all
Despite high blood sugar levels, you may have no symptoms at all before you receive a diabetes or prediabetes diagnosis, says Dr. Rettinger. When blood sugar is elevated but not high enough to be considered diabetes, the diagnosis is prediabetes.

“Most often the progression from prediabetes to diabetes takes many years, so getting your hemoglobin A1C checked every three years would find diabetes in its earliest stages,” Rettinger says. The A1C blood test is a measure of how much glucose attaches to the hemoglobin in your red blood cells, on average, over the prior three months. Particularly if you fall into one of the risk categories, it’s a good idea to have your A1C checked periodically.

Tests Typically Used to Diagnose Type 2 Diabetes and Prediabetes

You have diabetes if your blood glucose after fasting (and before a meal) is 126 milligrams per deciliter (mg/dL) or higher; if two hours after a 75 gram oral glucose tolerance test (OGTT), it is 200 mg/dL or higher; or if your A1C is 6.5 or higher.

Hemoglobin A1C Test

The A1C test can be used to diagnose prediabetes and diabetes.

“Because it is a measure of the patient’s average blood sugar over the previous three months, it gives much more information than simply getting a few blood sugar readings on the spot and is useful as an initial baseline as the patient gets treated,” says Rettinger. A 6.5 or higher result on two separate days is in the range of diabetes, while a result of 5.7 to 6.4 is in the prediabetes range.
How often you are tested once you receive a diagnosis depends on a number of factors. Typically, if you have prediabetes, you will be tested once a year. If you have type 2 diabetes, you will often be tested twice a year — though that might go up to four times a year if you use insulin to manage your blood sugar or if you otherwise have trouble stabilizing your blood sugar.

Keep in mind that the A1C test may not be accurate in people who have anemia or other disorders that affect red blood cell turnover. Additionally, people of Mediterranean, Southeast Asian, or African descent may have results that are falsely high or low because they have less common forms (variants) of hemoglobin in their blood.

For instance, people of African descent are more likely than those in other groups to have a hemoglobin variant that carries the sickle cell trait.

That variant also gives falsely low A1C readings, according to a retrospective cohort study published in 2017.

Other tests besides A1C are used to diagnose diabetes. After taking a medical history, which would determine any family incidence of the disease, your doctor may order lab tests to measure your blood glucose levels. A healthcare professional can make a diagnosis on the basis of two abnormal test results from the same blood sample or two separate results from different dates.

Fasting Plasma Glucose Test

This test is conducted in a doctor’s office on blood drawn after an eight-hour fast with no food or drink except water. The blood is normally drawn in the morning before you have eaten breakfast. You will be diagnosed according to the following parameters:

  • Normal blood sugar is less than 100 mg/dL.
  • Prediabetes (impaired fasting glucose) is from 100 to 125 mg/dL.
  • Diabetes is 126 mg/dL or higher.

Oral Glucose Tolerance Test

The OGTT is another diabetes test performed after you haven’t eaten for about eight hours. It allows your doctor to see how quickly glucose is cleared from your blood.

The technician will take a sample of your blood and then give you a prepared sugary drink. You will then have your blood drawn every hour, so that you will end up with blood glucose level results after:

  • Fasting
  • One hour after ingesting the sugary drink
  • Two hours after ingesting the sugary drink
  • Sometimes three hours after ingesting the sugary drink
You will be diagnosed according to the following parameters:

  • Normal blood sugar at two hours after testing is less than 140 mg/dL.
  • Prediabetes (impaired glucose tolerance) is 140 to 199 mg/dL.
  • Diabetes is 200 mg/dL or above.
The OGTT is also used in screening pregnant women for gestational diabetes and is usually performed between 24 and 28 weeks of pregnancy.

The OGTT is one of the best detectors of diabetes and prediabetes, but it is given less often in nonpregnant adults because it is more expensive to perform and not as easy to administer as some other tests.

Random Plasma Glucose Test

This test may be done at any time to measure blood sugar levels, usually when you have severe diabetes symptoms. It allows for the identification of high blood levels immediately, but it should not be used as a tool to diagnose diabetes.

Still, it can indicate that you need additional testing or treatment if your blood sugar is at least 200 mg/dL. The other classic symptoms of high blood sugar are:

  • You’re urinating more than usual.
  • You’re drinking more fluid than you normally do.
  • You’ve lost weight when you didn’t mean to.
Any diagnosis is generally confirmed with two results from a fasting plasma glucose test, an oral glucose tolerance test, or an A1C test.

What to Do if You Receive a Prediabetes or Diabetes Diagnosis

Once you have received a diagnosis of type 2 diabetes, it’s important to get a handle on your blood sugar level. Rettinger stresses the importance of preventing diabetes complications by keeping A1C on target.

The best A1C is different for everyone with diabetes, but here are some general targets:

  • Less Than 6.5 This may be an appropriate goal for younger patients, those who are at a low risk for bouts of hypoglycemia, and those who are not mixing too many medicines, among other individuals. It is also a goal for women who are trying to conceive or to reduce the risk of birth defects, excessive birth weight, preeclampsia, and other complications if they become pregnant.

  • Less Than 7 This a reasonable goal for many other nonpregnant adult women.

  • Less Than 7.5 This may be appropriate for older adults who are otherwise generally healthy with no other health complications.

  • Less Than 8.5 This may be appropriate for older adults with multiple other chronic illnesses and cognitive impairment.

These complications may arise if you don’t stick to those goals:

Your healthcare team will guide you in devising a plan for lowering your blood sugar and sticking to your goals. That team may include your primary care doctor, an endocrinologist, a certified diabetes care and education specialist (CDCES) or registered dietitian, and other doctors who can address health complications, such as a podiatrist.

It’s really important to meet with a dietitian, especially one who specializes in prediabetes or diabetes, says Rettinger. They can help you understand how to best control your blood sugar but still enjoy the foods that you love. “Diet control is not about extreme avoidance of any sugars or carbs,” she says. “It’s usually about moderation and portion control.”

You may end up limiting the amount of sweets, beverages, and food with added sugar that you consume while favoring appropriate portions of whole grains, vegetables, fruits, and lean or plant-based protein sources.

Furthermore, getting at least 150 minutes of exercise per week is an important part of managing diabetes well.
“It’s also important to discuss next steps with your primary care doctor and endocrinologist, if needed. These days, diabetes can be controlled with the proper medication and lifestyle changes,” Rettinger says. Your treatment plan may include home blood sugar monitoring, oral medication, and insulin.

Your healthcare provider may also assess your risk for cardiovascular disease annually, because that is a standard of care for all people with diabetes.

And if you receive a prediabetes diagnosis, don’t resign yourself to the idea that you will get type 2 diabetes. Losing only 5 to 7 percent of your weight and getting regular exercise can help you delay or prevent getting the disease.

For some, taking the common oral diabetes medication metformin (Glucophage) can also help delay or prevent the disease, says Rettinger. The medication should be considered for people with prediabetes who are obese, are over age 60, or have a history of gestational diabetes.

Whether you receive a diabetes or prediabetes diagnosis, seek out support if you need it. That means asking for help from loved ones, getting emotional help from a professional, or joining a diabetes support group.

Additional reporting by Stephanie Bucklin and Ingrid Strauch.

Check out Diabetes Daily’s article “10 Most Common Questions Answered After a Type 2 Diabetes Diagnosis”for the need-to-know facts after a diagnosis.

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