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.

Why It Is Done

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.

How To Prepare

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?).

How It Is Done

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.

How It Feels

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.