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What are ketones, and why are they dangerous?

Ketosis, or the process of burning ketones, has become a familiar buzzword—thanks to the popular low-carb ketogenic diet. Before this fad diet exploded across the U.S., ketones were really only known to healthcare professionals and those with diabetes—and were not necessarily a good thing. Here, learn what ketones are, and how they can be dangerous.

What are ketones?

“Ketones are water-soluble molecules that are produced by the liver. They are formed from fatty acids within the body when your body doesn’t produce enough insulin to convert glucose into energy,” says David Nazarian, MD, of My Concierge MD in Beverly Hills. 

Simply put, ketones (or ketone bodies) are an alternative fuel that is made in your liver when there is not enough glucose (sugar) for energy. When your body doesn’t have enough sugar or glucose for energy, your body needs a new energy source. Your body will then switch to breaking down fat for energy. This process is done in the liver, where fats are turned into a chemical called ketones. The ketones, a fatty acid, are then released from the liver and go into your bloodstream and are used as fuel to drive the body’s metabolism and to support muscle function. 

The body typically needs ketones when insulin levels are low. Examples of times when your body produces this alternative energy source include fasting, eating low-carb diets, or overnight when sleeping. 

In uncontrolled type 1 diabetes, ketones may be produced due to lack of insulin-producing beta cells of the pancreas or a lack of an exogenous, or outside, insulin source.

Measuring ketone production can be done with urine testing. The safe amount of ketones in urine varies from person to person and depends on their underlying health conditions. While some people can have ketones in their urine and it is normal, others should be concerned if there is a ketone build-up as this could be indicative of a more serious problem.

What is the most accurate way to measure ketones?

A blood meter or at-home urine test kit can are helpful in assessing ketones. The urine kit typically comes with a cup and test strips that you dip into the urine. The most accurate way to measure ketones, the gold standard in healthcare, is through a blood ketone meter (note: a glucose meter does not measure the same thing).

How often should you check ketones?

People newly diagnosed with diabetes should check their levels twice daily when they are first diagnosed. For those without diabetes, who want to measure ketones for weight-loss reasons, 0.5 mmol/L in blood or urine means you’ve achieved ketosis. 

Are ketones dangerous?

For those without diabetes, it’s not typically an issue when your body produces ketones. However, for people with diabetes, ketones can be very dangerous. This is because the body can’t regulate insulin, glucagon, and other hormones in those with diabetes. 

“High levels of ketones can be dangerous and can cause health issues. Dangerously high levels of ketones in our bodies usually occur in insulin-dependent diabetic type one patients who do not take their insulin,” said Dr. Nazarian, “It can lead to dehydration and can also change the chemical balance of your blood. Your blood becomes more acidic which if not corrected can lead to a coma or death.”

This chart explains healthy and dangerous ranges of ketones: 

Negative ketones Less than 0.6 millimoles per liter (mmol/L)
Low to moderate 0.6 to 1.5 mmol/L
High 1.6 to 3.0 mmol/L
Very high greater than 3.0 mmol/L


If your levels are low-moderate, call your doctor to discuss these levels to receive further testing. At your visit, your doctor will likely perform a urine or blood test to determine ketone levels and perform a blood sugar test. For levels greater than 1.6 it is important to seek emergency attention as symptoms could be life-threatening. 

Symptoms of high ketones

Symptoms associated with high ketone levels typically include:

  • Unquenchable thirst
  • Frequent urination
  • Dry mouth (xerostomia)
  • High blood sugar levels (over 240)

Untreated symptoms could progress to additional and more serious symptoms including:

  • Confusion or difficulty focusing
  • Fatigue
  • Nausea
  • Vomiting
  • Dry or flushed skin
  • Difficulty breathing
  • Breath characterized by a fruity smell
  • Abdominal pain

Diabetic ketoacidosis (DKA) is a serious complication of diabetes and can be a result of unaddressed ketone levels. This will cause blood to become acidic. This is a serious and life-threatening issue that can lead to brain swelling, diabetic coma or death. 

What if my ketones are too high?

If your levels are too high based on ketone testing, it is important to seek emergency medical treatment. You will likely have the symptoms listed above and it is possible it could lead to DKA. 

A medical professional will treat this condition within a hospital. Some common ways to treat are: 

  • IV fluids to help the patient from becoming dehydrated due to frequent urination
  • Electrolyte replacement to help boost the lost electrolytes. 
  • Insulin helps the body convert back to running on glucose instead of ketones for energy. 

Diabetes management is the best way to prevent high levels, which can be done by:

  • Checking blood glucose levels regularly
  • Eating a healthy diet
  • Checking for ketones if blood sugar is above 240 mg/dl
  • Managing correct insulin dosages

While people without diabetes can have ketones in the urine, DKA is only an issue for those with diabetes.