Creatinine Clearance (from forearm blood sample)

What Is Creatinine Clearance?

Creatinine clearance is a measure of how well your kidneys filter waste products like creatinine from your blood. Unlike a single blood test, this test uses a timed urine sample to determine how effectively your kidneys are working over time. It helps doctors assess kidney function and monitor conditions that may affect kidney health, such as diabetes or high blood pressure.

How Is This Test Done?

For this test, a small blood sample is taken from your forearm (venipuncture). You’ll also provide a 24-hour urine collection to measure the amount of creatinine excreted over that period. Your healthcare provider will guide you on how to properly collect your urine sample to ensure accurate results.

Why Might You Need This Test?

Your doctor may order creatinine clearance if they suspect kidney disease, evaluate kidney function before or after treatment, or monitor chronic conditions like diabetes or heart disease that can impact kidney health. It’s also used in certain medical procedures to assess kidney function before surgery or interventions.

What to Expect Before the Test

No special preparation is usually needed for the blood draw, but you may be asked to drink extra water if your urine sample requires a specific volume. For the 24-hour urine collection, follow your doctor’s instructions carefully—collect all urine for 24 hours, including at night, and keep it refrigerated until you return it to the lab.