Creatinine

The Test Sample

What is being tested?

Creatinine is produced in your muscles when a compound called creatine spontaneously breaks down. Creatine is used in a process in body cells to produce the energy needed to contract muscles and it is produced at a relatively constant rate. Almost all creatinine is excreted by the kidneys, so blood levels are a good measure of how well your kidneys are working.

How is the sample collected for testing?

A blood sample is taken from a vein in the arm. You may be asked to collect a complete 24-hour urine sample in addition to having your blood taken (see "Creatinine Clearance"). Your doctor or the laboratory will give you a large container and instructions for properly collecting this sample. You will normally be asked to collect urine as soon as you wake up in the morning until the same time the following day.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

If you don't know what a word or a medical term means, try the Mondofacto Online Medical Dictionary .