“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.
Ketones are a chemical byproduct created when your body breaks down fat for energy because it doesn't have enough carbs. Ketones are a direct result of low glucose.
Following a very low-carbohydrate diet can lead to high levels of ketones.
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.
At ZOE, we run the largest nutrition science study in the world. We believe that restrictive diets don’t work, and our research shows that following a personalized approach to food is more effective than following general advice.
You can learn more about our personalized nutrition program by taking our free quiz.
Join our mailing list
Sign up for fresh insights into our scientific discoveries and the latest nutrition updates. No spam, just science.
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.
Long-term results of the keto diet are mixed. Since it’s incredibly restrictive, it can be difficult to stick to. Plus, a high intake of saturated fat may raise your cholesterol levels.
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.
If you follow the keto diet, you’ll end up restricting some of the best sources of fiber available to you.
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.
The liver starts to quickly break down fat for energy, resulting in a buildup of ketones in the blood.
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.
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
low bone density and fractures
Ketoacidosis symptoms are more serious. The early symptoms are:
If you don’t receive treatment, ketoacidosis can quickly progress. It can cause:
fast, labored breathing
dry skin and mouth
muscle stiffness or aches
nausea and vomiting
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’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.
If an insulin pump is clogged or you take the wrong dose, you may also be at risk.
In some cases, ketoacidosis can be the first sign of diabetes.
Other causes of ketoacidosis can include:
a heart attack
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.
Ketosis typically occurs when people follow the keto diet, while ketoacidosis nearly always affects people with diabetes.
If you have symptoms and aren’t sure whether it’s ketosis or ketoacidosis, you can test your ketone levels at home with an over-the-counter blood or urine ketone test.
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.
If your ketone levels are high and you’re worried, contact a healthcare professional for advice.
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.
Eating plenty of plant-based foods is essential for the health of your gut microbiome.
To make sure your diet is well-balanced, try to eat lean protein, like fish or chicken, as well as non-starchy fruits and vegetables, like zucchini, cauliflower, broccoli, and avocado.
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.
Join the community
Be the first to know about ZOE’s breakthrough research, content from the world’s leading scientists, and more.
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.
If you have diabetes, it’s important to know the symptoms and treatments of ketoacidosis. Ask a healthcare professional for more information.
A case of hypoglycemia associated with the ketogenic diet and alcohol use. Journal of the Endocrine Society. (2020). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7278276/
Breath acetone as a potential marker in clinical practice. Journal of Breath Research. (2017). https://iopscience.iop.org/article/10.1088/1752-7163/aa66d3
Diabetic ketoacidosis. (2022). https://www.cdc.gov/diabetes/basics/diabetic-ketoacidosis.html
Diabetic ketoacidosis. (2023). https://www.nhs.uk/conditions/diabetic-ketoacidosis/
Effect of a plant-based, low-fat diet versus an animal-based, ketogenic diet on ad libitum energy intake. Nature Medicine. (2021). https://pubmed.ncbi.nlm.nih.gov/33479499/
Ketoacidosis associated with low-carbohydrate diet in a non-diabetic lactating woman: A case report. Journal of Medical Case Reports. (2015). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4591635/
Ketogenic diets and ketone supplementation: A strategy for therapeutic intervention. Frontiers in Nutrition. (2022). https://www.frontiersin.org/articles/10.3389/fnut.2022.947567/full
Low carbohydrate diet. StatPearls. (2023). https://www.ncbi.nlm.nih.gov/books/NBK537084/
Nutritional ketosis for weight management and reversal of metabolic syndrome. Current Nutrition Reports. (2018). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6472268/
Review of current evidence and clinical recommendations on the effects of low-carbohydrate and very-low-carbohydrate (including ketogenic) diets for the management of body weight and other cardiometabolic risk factors. Journal of Clinical Lipidology. (2019). https://www.lipidjournal.com/article/S1933-2874(19)30267-3/fulltext
Type 1 diabetes. (2017). https://www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes/type-1-diabetes