During the serum creatinine test, a member of your health care team takes a sample of blood by inserting a needle into a vein in your arm. The blood sample is sent to a lab for analysis. You can return to your usual activities immediately.
In some cases, your doctor may measure the level of creatinine in your urine as well. For this test, part of a creatinine clearance test, your doctor may ask you to collect 24 hours' worth of urine in a special container and submit it for analysis. The urine creatinine test can help your doctor more accurately assess the presence or degree of kidney failure.