24-Hour Urine Creatinine Clearance Test
Direct measurement of kidney function from complete urine collection
Last updated on: June 29, 2025
24-Hour Urine Collection Calculator
What is a 24-Hour Urine Creatinine Clearance Test?
Unlike estimated calculators, this test directly measures how much creatinine your kidneys clear in 24 hours. It requires collecting all urine for a full day and a blood test during that period.
This method is considered more accurate than formulas like Cockcroft-Gault when precise measurement is needed, as it measures actual creatinine excretion rather than estimating it.
When is a 24-Hour Urine Test Needed?
- **Unusual Body Size**: For patients with very high or low muscle mass where estimation formulas fail.
- **Dietary Factors**: Vegetarians, vegans, or people with unusual creatinine production.
- **Critical Drug Dosing**: When exact kidney function is needed for toxic medications like chemotherapy.
Interpreting Your 24-Hour Creatinine Clearance Result
Normal Direct Measurement (≥ 90 mL/min/1.73m²):
Your kidneys are clearing creatinine normally. This direct measurement confirms normal function.
Mild Reduction (60-89 mL/min/1.73m²):
Direct measurement shows mild impairment. Consider repeating in 3-6 months.
Moderate Reduction (45-59 mL/min/1.73m²):
Confirmed moderate impairment. Requires medical evaluation and monitoring.
Moderate to Severe Reduction (30-44 mL/min/1.73m²):
Significant impairment confirmed by direct measurement. Nephrology consultation advised.
Severe Reduction (15-29 mL/min/1.73m²):
Severe kidney damage confirmed. Prepare for renal replacement therapy planning.
Kidney Failure (< 15 mL/min/1.73m²):
End-stage renal disease confirmed by direct measurement. Immediate specialist care needed.
Ensuring Test Accuracy
The value of this 24-hour urine creatinine clearance test depends entirely on proper collection:
- Follow timing precisely: 24 hours means exactly 24 hours
- Keep container cold: Refrigeration prevents bacterial growth
- Include all urine: Even small amounts affect accuracy
- Avoid contamination: Keep feces out of collection
- Maintain normal activities: Don't alter diet or exercise during collection
- Record exact times: Start and end times must be precise
- Transport quickly: Deliver to lab within 2 hours of completion
This page has been medically reviewed by Dr. Khoulah Attia – PharmD, Immunology Specialist.