Ketones

A ketone test checks for ketones in your blood or urine. Ketones are substances that are made when the body breaks down fat for energy. Normally, your body gets the energy it needs from carbohydrate in your diet. However, stored fat is broken down and ketones are made if your diet does not contain enough carbohydrate to supply the body with sugar (glucose) for energy or if your body cannot use blood sugar (glucose) properly.

Newer home blood sugar meters can also measure ketones. Home urine tests to measure ketones are available.

A blood test is the most accurate method of measuring ketones. It is recommended for all people with diabetes whenever symptoms of illness are present, such as nausea, vomiting, or abdominal pain. These symptoms are similar to symptoms of high blood sugar and may mean you have diabetic ketoacidosis, a potentially life-threatening condition.

A urine test is the most commonly used method of measuring ketones. But it is less accurate than a blood test. It may be done to:

• Monitor a person on a very low-carbohydrate diet.
• Monitor a pregnant woman who has diabetes or has developed gestational diabetes.

No special preparation is needed before having this test.

Talk to your health professional about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will indicate. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

Blood test

The health professional taking a sample of your blood will:

• Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
• Clean the needle site with alcohol.
• Put the needle into the vein. More than one needle stick may be needed.
• Attach a tube to the needle to fill it with blood.
• Remove the band from your arm when enough blood is collected.
• Apply a gauze pad or cotton ball over the needle site as the needle is removed.
• Apply pressure to the site and then a bandage.

Urine test

• Collect a urine sample in a clean container.
• Follow the manufacturer's directions on the bottle of test strips or tablets.
• Avoid getting toilet paper, pubic hair, stool, menstrual blood, or other foreign matter in the urine sample.

Blood test

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

Urine test

There is normally no discomfort involved with collecting a urine sample.

Blood test

There is very little risk of a problem from having blood drawn from a vein.

• You may develop a small bruise at the puncture site. You can reduce the risk of bruising by keeping pressure on the site for several minutes after the needle is withdrawn.
• In rare cases, the vein may become inflamed after the blood sample is taken. This condition is called phlebitis and is usually treated with a warm compress applied several times daily.
• Continued bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can also make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your health professional before your blood is drawn.

Urine test

There are no risks associated with collecting a urine sample.

A ketone test checks for substances made when the body breaks down fat for energy (ketones).

Urine test

If either the test strip or the urine changes color when the tablet is dropped into the sample, ketones are present in your urine sample. The test results are read as negative to 1+ to 4+ or small to large.

High values

You may have ketones in your urine if you:

• Have poorly controlled diabetes or diabetic ketoacidosis.
• Are on a very low-carbohydrate diet.
• Are starving or have an eating disorder, including disorders that result in poor nutrition such as anorexia nervosa or bulimia, alcoholism, or poisoning from drinking rubbing alcohol (isopropanol).
• Have not eaten (fasted) for 18 hours or longer.
• Are pregnant. However, a moderate amount of ketones in a pregnant woman may harm the fetus and may be an indication of gestational diabetes.

The level of ketones, and not just the presence of ketones, may be important to your doctor as well. Many conditions can change ketone levels. Fasting usually causes only mild increases in the level, but ketone levels in diabetic ketoacidosis are much higher. Your health professional will discuss any significant abnormal results with you in relation to your symptoms and medical history.

Reasons you may not be able to have the test or why the results may not be helpful include:

• Taking medicines, such as:
  • Levodopa, such as Sinemet or Larodopa.
  • Phenazopyridine, such as Pyridium, Geridium, Pyridiate, or Urogesic.
  • Valproic acid, such as Depakote, Depacon, or Depakene.
  • Vitamin C (ascorbic acid), when taken in large amounts.
• Dehydration.
• A high-fat diet.
• Pregnancy.

• The blood test can check for one type of ketone that the urine test cannot detect. Therefore, a urine test that does not show any ketones may not be accurate (false-negative result).
• Ketone levels will increase in your urine before they increase in your blood if you are fasting or on a very low carbohydrate diet.
• The American Diabetes Association recommends that you test your urine for ketones if you have diabetes and you:
  • Are pregnant.
  • Are sick or feeling very stressed.
  • Have blood sugar levels of 300 mg/dL (16.7 mmol/L) or higher.
  • Have symptoms of high blood sugar (diabetic ketoacidosis), such as nausea, vomiting, or abdominal pain.
• Ketones can be tested at home using urine ketone test strips. A more accurate reading can be obtained by some home glucose meters that test for blood ketones.

Other Works Consulted

• Chernecky CC, Berger BJ, eds. (2004). Laboratory Tests and Diagnostic Procedures, 4th ed. Philadelphia: Saunders.

• Fischbach FT, Dunning MB III, eds. (2004). Manual of Laboratory and Diagnostic Tests, 7th ed. Philadelphia: Lippincott Williams and Wilkins.

• Handbook of Diagnostic Tests (2003). 3rd ed. Philadelphia: Lippincott Williams and Wilkins.

• Pagana KD, Pagana TJ (2002). Mosby’s Manual of Diagnostic and Laboratory Tests, 2nd ed. St. Louis: Mosby.