Serum ketones

Alternative names
Acetone bodies; Ketones - serum; Nitroprusside test; Ketone bodies - serum

Definition
This test measures the amount of ketones in the blood. Any amount of detectable ketones is considered abnormal.

How the test is performed

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band or blood pressure cuff is placed around the upper arm to cause the veins below the band to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children:
The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

How to prepare for the test
Fast for 4 hours before the test.

For infants and children, the preparation you can provide for this test depends on your child’s age, previous experience, and level of trust. For general information on how you can prepare your child, see the following:

     
  • infant test or procedure preparation (birth to 1 year)  
  • toddler test or procedure preparation (1 to 3 years)  
  • preschooler test or procedure preparation (3 to 6 years)  
  • schoolage test or procedure preparation (6 to 12 years)  
  • adolescent test or procedure preparation (12 to 18 years)

How the test will feel
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed

This test is used to diagnose ketoacidosis, which is high levels of ketones in the blood. The main causes of ketoacidosis are uncontrolled diabetes, starvation, and alcoholism.

In diabetes, there may not be enough insulin to move glucose into cells. The body then looks for other forms of energy and uses fat as a fuel source. As fats are broken down, acids called ketones build up in the blood and urine. In high levels, ketones are poisonous to body tissue.

The diagnosis is often made in an urgent care center of an emergency department. A patient suspected of having ketoacidosis may have already had a urine test showing ketones in the urine, or a blood test showing low levels of bicarbonate, indicating acid in the blood.

Normal Values
A normal test result would be “negative”, meaning there are no ketone bodies in the blood.

What abnormal results mean
A test result is “positive” if ketones are found in the blood. This may indicate:

     
  • alcoholic ketoacidosis  
  • starvation  
  • uncontrolled blood glucose in diabetics

What the risks are

The only risks are those associated with the venipuncture.

Special considerations
A diet low in carbohydrates can increase ketone bodies.

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Johns Hopkins patient information

Last revised: December 3, 2012
by Martin A. Harms, M.D.

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