Urinary Creatinine to Glomerular Filtration Rate (GFR) Ratio (24-hour collection)

Why This Test Is Done

Your doctor may order this test if they suspect kidney disease, monitor kidney function over time, or check for conditions affecting how well your kidneys filter blood, such as diabetes or high blood pressure. It can also help assess kidney function in people with chronic conditions or after certain treatments.

What to Expect Before the Test

You’ll need to collect all urine for a full 24-hour period (typically from one morning to the next). Drink plenty of fluids to ensure your urine is well-mixed. Your doctor or lab technician will provide detailed instructions on how to properly collect your urine sample.

What Happens During the Test

After your urine is collected, it will be tested in a lab to measure creatinine levels. Your GFR is estimated using a standard formula that considers your age, sex, and blood creatinine levels (often measured separately). The ratio helps determine how efficiently your kidneys are filtering waste.

What the Results Mean

The results compare your urine creatinine output to your estimated GFR. A lower ratio may indicate reduced kidney function or impaired filtering ability, while a higher ratio may suggest overproduction of creatinine or other conditions affecting kidney health. Your doctor will interpret these results in the context of your overall health.