What is being tested?
This test measures the amount of creatinine in your blood and/or urine. Creatinine is a waste product produced in your muscles from the breakdown of a compound called creatine. Creatine is part of the cycle that produces energy needed to contract your muscles and it as well as creatinine are 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. The quantity produced depends on the size of the person and their muscle mass. For this reason, creatinine concentrations will be slightly higher in men than in women and children.

How is the sample collected for testing?
A blood sample is drawn from a vein in the arm. You may be asked to collect a complete 24-hour urine sample in addition to having your blood drawn. Your doctor or the laboratory will give you a large container and instructions for properly collecting this sample. Typically, you start collecting urine after you wake up in the morning and empty your bladder and save all of the urine produced until the same time the following day.

Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.