At a Glance
Why Get Tested?
To determine if your kidneys work normally and to monitor treatment for kidney disease
When to Get Tested?
As part of a routine blood test if you have non-specific health complaints or if your doctor thinks that you may have kidney disease; at intervals to monitor treatment for kidney disease or kidney function while on certain medicines
A blood sample drawn from a vein in the arm.
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 produces creatinine at a fairly 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 drawn from a vein in the arm. In rare cases you may be asked to collect a complete 24-hour urine sample in addition to having your blood taken (see creatinine clearance). If this is required 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.
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.