Ketones - urine

Alternative names
Ketone bodies - urine; Urine ketones: acetone, acetoacetic acid, and beta-hydroxybutyric acid

Definition
A ketones urine test measures the presence or absence of ketones in the urine.

How the test is performed
Child or adult:
Collect a “clean-catch” (“midstream”) urine sample. To obtain a clean-catch sample, men or boys should wipe clean the head of the penis. Women or girls need to wash the area between the lips of the vagina with soapy water and rinse well. As you start to urinate, allow a small amount to fall into the toilet bowl (this clears the urethra of contaminants). Then, in a clean container, catch about 1 to 2 ounces of urine and remove the container from the urine stream. Give the container to the health care provider or assistant.

Infant:
Thoroughly wash the area around the urethra. Open a Urine collection bag (a plastic bag with an adhesive paper on one end), and place it on your infant. For males, the entire penis can be placed in the bag and the adhesive attached to the skin. For females, the bag is placed over the labia. Diaper the infant as usual, covering and securing the bag. Check the baby frequently and remove the bag after the infant has urinated into it. Active infants may displace the bag, so it may take more than one attempt to obtain the specimen. Drain the urine into a container and give it to the health care provider.

Urine ketones are usually measured as a “spot test” with a dipstick containing a color-sensitive pad impregnated with specific chemicals which react with ketone bodies. A color change is a qualitative indicator of the presence of ketones.

How to prepare for the test
A special diet may be recommended, and drugs that may affect the test results should be discontinued (see Special Considerations).

If the collection is being taken from an infant, a couple of extra collection bags may be necessary.

How the test will feel
The test involves only normal urination, and there is no discomfort.

Why the test is performed
Ketones (beta-hydroxybutyric acid, acetoacetic acid, and acetone) are the end-product of rapid or excessive fatty acid breakdown. As with glucose, ketones are present in the urine when the blood levels surpass a certain threshold. Fatty acid release from adipose tissue is stimulated by a number of hormones including glucagon, epinephrine, and growth hormone. The levels of these hormones are increased in starvation (whether related to excess alcohol use or not), uncontrolled diabetes mellitus, and a number of other conditions.

Normal Values

A negative test result is normal. Results of the presence of acetone in the urine are usually listed as small, moderate or large with these corresponding values:

Small - < 20 mg/dL

Moderate - 30-40 mg/dL

Large - >80 mg/dL

What abnormal results mean
A positive test may indicate:

     
  • Metabolic abnormalities, including uncontrolled diabetes or glycogen storage disease  
  • Abnormal nutritional conditions, including starvation, fasting, anorexia, high protein or low carbohydrate diets  
  • Protracted vomiting, including hyperemesis gravidarum  
  • Disorders of increased metabolism, including hyperthyroidism, fever, acute or severe illness, burns, pregnancy, lactation or post-surgical condition

What the risks are
There are no risks.

Special considerations
Special diets may alter test results. For example, a diet consisting of low amounts of carbohydrates with high amounts of protein and fat may effect the ketone levels.

Drugs that may cause false positive measurements include glucocorticoids.

Johns Hopkins patient information

Last revised: December 5, 2012
by David A. Scott, M.D.

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