Serum/Plasma Creatinine with 24-Hour Urine Creatinine Clearance

Why This Test Matters for Kidney Health

Kidneys play a vital role in removing waste and excess fluids from your blood. This test evaluates how efficiently they do this by measuring creatinine levels in your blood and urine over a full day. Creatinine is a waste product from muscle metabolism that kidneys normally filter out. If your kidneys aren’t working well, creatinine builds up in your blood, which can indicate kidney problems.

Blood Test: Measuring Creatinine Levels

A blood sample is taken to measure your baseline creatinine level. This helps determine your glomerular filtration rate (GFR), a measure of kidney function. Higher blood creatinine levels (when compared to expected values) may suggest reduced kidney function.

Urine Test: Collecting 24-Hour Sample

You’ll need to collect all urine for a full 24-hour period in a special container. This urine sample is tested for creatinine to see how much your kidneys are filtering over time. The ratio of creatinine in your urine to blood helps calculate your creatinine clearance, which reflects kidney function.

What to Expect During Testing

For the blood test, a simple vein puncture is done at a lab or your doctor’s office. For the urine test, you’ll need to collect every drop of urine for 24 hours, starting and ending with a sample. Follow your healthcare provider’s instructions carefully to ensure accuracy.