Ketosis and ketoacidosis sound similar and are sometimes confused, but don’t mistake these conditions for one another. These involve two different sets of circumstances with considerably different outlooks.

Both are triggered by an increase of ketones in the body, which are acids released into the bloodstream when the body burns fat for energy instead of carbohydrates. But it’s how the body responds to this increase that sets ketosis and ketoacidosis apart from each other.

What Is Ketosis and How Does the Process Work?

“Ketosis is a natural state that occurs when you start to metabolize fat instead of sugar,” says Michael Greenfield, MD, endocrinologist and chief medical officer at El Camino Hospital in Palo Alto, California. “It occurs often when people fast and use up the stores of sugar in their body."

To understand ketosis, it helps to understand how the body burns energy. Carbohydrates and fat are both energy sources, and the body typically burns carbs (sugar or glucose) first, and then fat. If there aren’t enough carbohydrates in your system, it begins to break down fat for energy, which puts your body into a state of ketosis.

While in this state, the body becomes a fat-burning machine. For this reason, ketosis is the goal of many diets, particularly those that restrict carbohydrate intake and rely on fat for energy, such as the ketogenic diet.

Understanding the Relationship Between the Ketogenic Diet and Ketosis

“The ketogenic diet is a high-fat (60 to 80 percent of your total daily calories), moderate-protein (10 to 15 percent of your total daily calories), and low-carbohydrate diet (less than 10 percent of your total daily calories) that forces your body into ketosis, where it burns fat as its primary source for energy,” says Deborah Malkoff-Cohen, RD, CDE, and founder of City Kids Nutrition, a nutritional consultation service for children in New York City. “Think of the old Atkins plan where your ex-boyfriend would eat slabs of bacon, eggs, and a porterhouse steak, and lose 21 pounds in a month.”

But although the ketogenic diet is similar to Atkins, it’s not the same. Atkins is a high-protein diet, whereas the ketogenic diet is a high-fat diet.

Malkoff explains that the ketogenic diet works by rewiring metabolism so that it can burn fat more efficiently over time, and it uses specific levels of macronutrients (fats, carbs, and proteins) to keep the body in a constant state of ketosis. Because the body can only go into ketosis when it’s using fat for fuel, this is a hard diet to follow, and it often means saying goodbye to starchy veggies, like potatoes, rice, corn, squash, dairy, some fruits, bread, and beans that are too carb-y, she says. The plan has become popular among people with type 2 diabetes because of its potential to lower blood sugar while leading to weight loss.

For people who are able to stick with it, the ketogenic diet can reduce appetite and lower triglycerides — a form of fat that can affect heart-disease risk — while contributing to weight loss and sharper brain function. But this doesn’t mean the ketogenic diet is right for everyone. Particularly, people with kidney damage, women who are breast-feeding or pregnant, and some individuals on certain kinds of medication should avoid ketosis. It's important to discuss your diet goals with your doctor before trying to achieve this state.

Also important to note is there are no long-term studies on ketosis and the ketogenic diet, so it's unclear what health effects the approach may have on the body if sustained. Some dietitians warn the ketogenic diet may lead to nutritional deficiencies in the long run.

People with type 1 diabetes should not try to achieve ketosis through the ketogenic diet or otherwise. Because people with type 1 diabetes don't have insulin, they cannot metabolize ketones, which are gradually flushed through urine in people without the disease. For people with type 1 diabetes, ketosis can result in an accumulation of ketone acids in their bloodstream known as diabetic ketoacidosis (DKA), says Dr. Greenfield.

What Is Diabetic Ketoacidosis Exactly?

“[Ketoacidosis] is caused by a lack of insulin available for the cells to adequately uptake the sugar (glucose) in the blood to use for energy,” explains Malkoff-Cohen. “Without enough insulin, your body begins to break down fat for energy, and ketones are then released into the bloodstream, where they cause a chemical imbalance in the blood called metabolic acidosis.”

Whereas ketosis is natural and harmless, diabetic ketoacidosis can be life-threatening if left untreated. Too much acid in the blood can poison the body, causing loss of consciousness and death. Ketoacidosis is most common in people who have type 1 diabetes, but it can sometimes develop in type 2 diabetes due to low insulin levels.

Ketoacidosis is rare in people without diabetes, but it might occur in cases of starvation. A study published in October 2015 in the Journal of Medical Case Reports found that a low-carbohydrate diet combined with lactation could potentially induce ketoacidosis in women without diabetes, but more research is needed.

Poor diabetes management, or not having enough insulin in your system, is one cause of ketoacidosis. Other factors include developing an infection (such as pneumonia or a urinary tract infection), abusing drugs or alcohol, or taking a medication that affects how your body uses sugar. For example, corticosteroids, which are used for Crohn’s disease and asthma, among other health conditions, can make it harder for your cells to use insulin, whereas diuretics, used for controlling heart disease, can increase blood glucose levels.

Diabetic ketoacidosis can develop quickly, sometimes within 24 hours. The condition is responsible for more than 130,000 admissions to the hospital, as well as 50,000 hospital days per year in the United States, according to an article published in the journal Diabetes Management. According to an article published in March 2013 in American Family Physician, diabetic ketoacidosis is the leading cause of death among people with diabetes who are under age 24.

Symptoms of diabetic ketoacidosis include:

Excessive thirst
Frequent urination
Vomiting
Weakness
Shortness of breath
Fruity-smelling breath
Confusion

How to Treat Diabetic Ketoacidosis

If you have diabetes, not only should you monitor your blood sugar on a regular basis, you should also maintain a supply of ketone urine test strips, and then check your ketone level whenever your blood sugar rises above 250 milligrams per deciliter (mg/dL).

If test strips detect ketones in your urine, begin self-treatment by drinking plenty of fluids to flush ketones from your body, and then take insulin to bring down your blood sugar. If your ketone level doesn’t come down, or if you begin vomiting, go to the emergency room.

Hospital treatment involves rehydration to replace fluids lost through excessive urination or vomiting, electrolyte replacement to maintain heart, nerves, and cell function, as well as insulin therapy to regulate your blood sugar level. Your doctor may also screen for infections or modify your medication.

Tips to Prevent Ketoacidosis

Ketoacidosis is preventable in people who have type 1 and type 2 diabetes. To avoid this potentially life-threatening complication:

Take your diabetes medication as directed and don’t skip insulin doses.
Monitor your blood sugar and ketones every couple of hours while sick.
Drink plenty of fluids while sick to prevent dehydration, about 8 ounces of a caffeine-free beverage every hour.
Continue taking insulin while sick, even if you’re not eating a lot.

Physical activity is recommended for people with diabetes, but don’t forget to check your blood sugar level before a workout. Exercising with elevated blood sugar could trigger diabetic ketoacidosis.

A safe blood sugar level for exercise is 100 to 250 mg/dL. If your level is lower than 100 mg/dL, eat a preworkout snack to boost your blood sugar and energy (between 15 and 30 grams of carbs). Don’t work out if your blood sugar level is higher than 250 mg/dL.

The Takeaway on Ketosis vs. Diabetic Ketoacidosis

Ketosis and ketoacidosis may sound similar, but these conditions are totally different. Whereas the former can occur from eating a low-carbohydrate diet and isn’t harmful, the latter is a life-threatening complication of type 1 diabetes (and sometimes type 2 diabetes) that can cause a dangerous level of acid in the blood.

What’s the Difference Between Ketosis and Diabetic Ketoacidosis?