What’s the difference between ketosis and ketoacidosis?

“Ketosis” and “ketoacidosis” sound similar, but they’re very different.

Ketosis is a metabolic process that occurs when the body breaks down fat for energy if it's not getting enough carbohydrates. 

Ketoacidosis, meanwhile, is typically a life-threatening complication of diabetes. It happens when insulin levels drop dangerously low, causing a buildup of ketones and acid in the blood.

In the short term, ketosis may result in weight loss, flu-like symptoms, and tiredness.

Ketoacidosis occurs with serious complications. People who may have it need urgent medical attention. It's extremely rare in people who don't have diabetes.

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What is ketosis?

Your body typically gets energy from the glucose in carbs. When someone reduces their carbohydrate intake to a very low level, their body breaks down fat instead.

Ketosis can also result from long periods of fasting or taking ketone supplements.

In the short term, ketosis has some unwanted side effects, such as: 

• “Keto flu”: Symptoms include headaches, aching muscles, and fatigue.

• “Keto breath”: Ketones are acidic and can cause bad breath.

• Constipation: Removing high-fiber foods from your diet can lead to constipation.

• Low blood sugar: A low carb consumption can lead to low blood sugar, causing dizziness, headaches, and heart palpitations. 

Research suggests that the keto diet can help some people lose weight in the short term, although some of this may be due to water loss.

A 2019 review looked at how well a variety of diets resulted in weight loss. It found that low- and very low-carb diets weren’t any more effective than others.

So, the keto diet doesn’t seem to offer clear, long-term benefits, compared to other approaches.

How long is it safe to be in ketosis for?

There isn’t a clear agreement among experts about  the safety of remaining in ketosis for a long period. 

However, many sources claim that the keto diet isn’t sustainable.

Fiber is vital for the health of your gut microbiome, the trillions of microbes that live in your gut and have a major impact on your overall health.

To learn more about the keto diet's effects on your body, check out the ZOE Science & Nutrition podcast on the topic.

What is ketoacidosis?

Ketoacidosis is a life-threatening complication of diabetes. It develops when the body doesn’t have enough insulin to take blood sugar into cells.

A fast production of ketones can overwhelm the body and cause the blood to become acidic. This is extremely dangerous. 

Can you get ketoacidosis if you don’t have diabetes?

In people who don’t have diabetes, ketoacidosis is extremely rare.

One case report described ketoacidosis in a person who followed a very low-carbohydrate, high-fat diet while lactating. It mainly occurs in people with diabetes. 

Symptoms

Ketosis and ketoacidosis have some symptoms that overlap, but many of the symptoms are different.

Here are some symptoms of ketosis: 

• bad or fruity-smelling breath, also known as “keto breath”

• “keto flu,” which may involve muscle aches, fatigue, and a headache

• constipation

• insomnia

• dehydration

• low bone density and fractures

• high cholesterol 

• kidney stones

Ketoacidosis symptoms are more serious. The early symptoms are:

• extreme thirst

• excessive urination

If you don’t receive treatment, ketoacidosis can quickly progress. It can cause: 

• fast, labored breathing

• dry skin and mouth

• flushed face

• headaches

• muscle stiffness or aches

• extreme fatigue

• nausea and vomiting

• abdominal pain

When to contact a doctor

For people at risk of ketoacidosis, it’s a good idea to use an over-the-counter urine or blood ketone test every 4–6 hours if: 

• You’re sick. 

• You’ve missed an insulin shot.

• You have any symptom of ketoacidosis.

• Your blood sugar is 240 milligrams per deciliter (mg/dL) or higher. 

If the test shows moderate or high levels of ketones, call your doctor for advice. We describe these levels below.

Go to the emergency room right away if any of these apply to you:

• You have diabetes, and your blood sugar stays at 300 mg/dL or above.

• You’re vomiting and unable to keep down food.

• You have trouble breathing.

• You have multiple symptoms of ketoacidosis.  

What causes ketoacidosis?

High blood sugar and low insulin levels cause ketoacidosis. These can happen when you’re ill or you’ve missed an insulin shot.

In some cases, ketoacidosis can be the first sign of diabetes. 

Other causes of ketoacidosis can include:

• a heart attack

• a stroke

• a traumatic injury, such as from a car accident

• alcohol or drug misuse

• certain medications, including some water pills and anti-inflammatories

But it’s worth remembering that ketoacidosis is extremely rare in people who don’t have diabetes.

Telling the difference

When you’re in ketosis, your blood ketone level is at least 0.5 millimoles per litre (mmol/L), which is around 9 mg/dL. 

If a person has ketoacidosis, this level is around 5–10 times higher.

As we’ve already seen, the symptoms of ketosis and ketoacidosis differ. In general, ketoacidosis causes more severe symptoms.

Doctors recommend that people with diabetes test their ketones if they’re feeling sick, have any symptom of ketoacidosis, or have a blood sugar level of 240 mg/dL (around 13 mmol/L) or higher.

Normal ketone levels can vary from person to person. Your diabetes care team can let you know if there’s a certain level to aim for.

Here are some general guidelines:

Blood ketone levels:

• Normal range: 10.8 mg/dL (0.6 mmol/L) or below

• Slightly high, retest in 2 hours: 10.8–27 mg/dL (0.6–1.5 mmol/L)

• High: 28.8–54 mg/dL (1.6–3 mmol/L)

• Seek urgent medical care: 54 mg/dL (3 mmol/L) or higher

Urine ketone levels:

A score of 2 or above on a urine test strip is high.

Treatment for ketoacidosis

Ketoacidosis requires treatment from a medical professional in a hospital. They’ll likely give you: 

• fluids to replace those lost in urination and to dilute the sugar in your blood

• salts and minerals called electrolytes

• insulin to bring up your blood sugar level

• any other medication needed to treat the cause of ketoacidosis

Healthcare providers will also check you for any complications, as ketoacidosis can affect your heart, brain, and lungs, in some cases.

Other keto diet considerations

The keto diet is extremely low in plant-based foods, since these foods tend to be higher in carbs. 

Eliminating these foods from your diet can reduce your intake of fiber, vitamins, minerals, antioxidants, and polyphenols. 

Keep in mind that other approaches to eating can help you reach your health goals. At ZOE, we believe that one-size-fits-all approaches and restrictive diets don’t work.

Instead, our at-home test will analyze your gut health and blood sugar and fat responses. With this information, our nutrition program provides personalized advice about the best foods for you and your health goals.

Find out how it works and take our free quiz.

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Summary

Ketosis and ketoacidosis both involve ketones, but they’re very different conditions.

Ketosis happens when you follow a keto diet. It can also occur after you fast or take certain supplements. 

On the other hand, ketoacidosis is a life-threatening complication that can develop in people with diabetes.