What are ketones and what causes them?

Ketones are the result of the body burning fat for energy or fuel. For a person with diabetes, ketones are often the result of prolonged high blood sugar and insulin deficiency. Without the right amount of insulin, glucose starts to build up in the blood stream and doesn't enter the cells. The cells burn fat instead of glucose, and ketones form in the blood and spill into the urine.

Some causes of high blood sugar are:


What are the signs that I should test for ketones?

Symptoms of high blood sugar include frequent urination, frequent thirst, blurry vision, dry mouth, vomiting, and fatigue.

There are several scenarios that should prompt a test for ketones.

  • If your blood sugar is over 240 mg/dl for two tests in a row.
  • When you are ill.
  • When your blood sugar is over 240 mg/dl and you are planning on exercising.
  • If you are pregnant, you should test for ketones each morning before breakfast and whenever blood sugars are elevated.

How do I test for ketones?

There are two ways to test for ketones - by testing your urine or your blood. Ketones appear first in the blood stream and are later present in the urine, so testing your blood for ketones is the best way to check for an early problem.

To check urine for ketones, you must collect a urine sample or dip a ketone test strip into a fresh stream of urine. After waiting for the time suggested by the ketone strip manufacturer, you compare the color strip to the chart on the bottle. The darker the color, the higher the amount of ketones in the urine.

At this time, there are just a few meters on the market that can test for blood ketones. These meters use a small drop of blood to measure the level of ketones and display the result on the meter screen.

What do I do if I have ketones?

If you test positive for ketones, it is important to carefully monitor your blood sugar and keep yourself hydrated. Drink plenty of water and other no-calorie fluids to help flush your system of ketones. Be sure to test your blood sugar every few hours and continue to test for ketones until your results come back negative. It is also important to refrain from exercising if you have ketones, as exercise will usually raise the level of ketones in your body. Spilling trace to moderate levels of ketones can usually be self-treated by closely monitoring and flushing your system. However, spilling large levels of ketones is reason to seek emergency care or to discuss your conditon with your health care team.

If you are not sure what to do to manage your high blood sugar and flush ketones from your system, you should consult your doctor immediately. The presence of ketones can quickly become a dangerous condition called DKA (Diabetic Ketoacidosis), which is a serious medical emergency, and requires prompt treatment. If you begin vomiting and/or have a high blood sugar that is not coming down despite medication, you should contact your doctor immediately.

Reviewed by Francine Kaufman, MD. 8/08

Last Modified Date: June 14, 2013

All content on is created and reviewed in compliance with our editorial policy.

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by Carey Potash
Yesterday was pretty horrible. Today is better. So far … Yesterday morning’s Dexcom graph was Mount Kilimanjaro. Today we have a dorsal fin, jutting out of the water at about 200 before descending into a connect-the-dots shark. He appears to be 63 at lunchtime versus three-hundred-something yesterday. Not perfect, but it never is. Charlie’s teacher and the nurse mentioned that he didn’t look like himself yesterday. He had taken too many body blows from diabetes...