Plasma or Serum Creatinine to Urine Creatinine Ratio (24-hour collection)

Why This Test Matters

Kidney function is critical for removing waste and excess fluids from your blood. This test provides a detailed picture of how well your kidneys are working by tracking creatinine levels in both your blood and urine over a full day. It can help detect early signs of kidney problems, including conditions like chronic kidney disease or kidney damage.

How the Test Works

You’ll collect urine for 24 hours, typically starting after a full night’s sleep. Your healthcare provider will provide instructions on when and how to begin and end the collection. Blood is drawn once to measure your creatinine level. The ratio of creatinine in your urine to blood helps determine how well your kidneys are filtering waste.

What to Expect Before the Test

No special preparation is needed for the blood draw, but you should follow your urine collection instructions carefully. Drink plenty of fluids during the day to help your kidneys produce urine. Avoid medications that may affect kidney function unless approved by your doctor.

What to Expect During the Test

The blood draw is quick and usually done in a clinic or lab. The urine collection requires careful timing and may involve a 24-hour period. If you miss any urine or have an accident, inform your healthcare provider immediately to ensure accurate results.