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Ketone Testing: What You Need to Know

What are ketones?

Ketones are produced when the body burns fat for energy or fuel. They are also produced when you lose weight or if there is not enough insulin to help your body use sugar for energy. Without enough insulin, glucose builds up in the blood. Since the body is unable to use glucose for energy, it breaks down fat instead. When this occurs, ketones form in the blood and spill into the urine. These ketones can make you very sick.

How can I test for ketones?

You can test to see if your body is making any ketones by doing a simple urine test. There are several products available for ketone testing and they can be purchased, without a prescription, at your pharmacy. The test result can be negative, or show small, moderate, or large quantities of ketones.

When should I test for ketones?

  • Anytime your blood glucose is over 250 mg/dl for two tests in a row.
  • When you are ill. Often illness, infections, or injuries will cause sudden high blood glucose and this is an especially important time to check for ketones.
  • When you are planning to exercise and the blood glucose is over 250 mg/dl.
  • If you are pregnant, you should test for ketones each morning before breakfast and any time the blood glucose is over 250 mg/dl.

If ketones are positive, what does this mean?

There are situations when you might have ketones without the blood glucose being too high. Positive ketones are not a problem when blood glucose levels are within range and you are trying to lose weight.

It is a problem if blood glucose levels are high and left untreated. Untreated high blood glucose with positive ketones can lead to a life-threatening condition called diabetic ketoacidosis (DKA).

What should I do if the ketone test is positive?

Call your diabetes educator or physician, as you may need additional insulin. Drink plenty of water and fluids containing no calories to "wash out" the ketones. Continue testing your blood glucose every 3 - 4 hours, testing for ketones if the blood glucose is over 250 mg/dl. Do not exercise if your blood glucose is over 250 mg/dl and ketones are present.

For more information, turn to Joslin's Guide to Diabetes.

Page last updated: April 17, 2014