Creatinine Clearance from 24-Hour Urine (CrCl)

Q: Why does CrCl overestimate true GFR?

Creatinine is filtered and also actively secreted by proximal tubules, so urinary creatinine clearance exceeds the true filtration rate by roughly 10–20%, with a larger gap at low GFR.

Q: How do I check whether the 24-hour collection was complete?

Compare the collection's total creatinine (urine creatinine × volume) with the expected daily excretion (~15–20 mg/kg/day in men, 10–15 mg/kg/day in women). Wide deviations suggest over- or under-collection.

Calculates creatinine clearance from a 24-hour urine collection using urine creatinine, serum creatinine, and 24-hour urine volume. It is the classic timed-collection estimate of GFR.

Nephrology NephrologyEvidence-BasedUpdated 2026-08-16

Clinical Notes

Formula

CrCl (mL/min) = (Urine Creatinine × 24h Urine Volume) ÷ (Serum Creatinine × 1440)

Normal Range

Approximately 85–125 mL/min in healthy young adults; declines with age

Clinical Notes

The timed 24-hour creatinine clearance is the classical bedside estimate of GFR. Because of collection errors and tubular creatinine secretion, it is less commonly used than estimating equations but remains useful in select settings (e.g., extremes of body habitus).

References

Levey AS, et al. Clin Chem. 2007;53(4):766-772.
Cockcroft DW, Gault MH. Nephron. 1976;16(1):31-41.

Calculator Information

Specialty

Nephrology

📋 Reference Ranges

Normal Range

Approximately 85–125 mL/min in healthy young adults; declines with age

Reference ranges for this calculator
Classification	Range
Normal young healthy adults (varies by age/sex)	≥90 mL/min
Mildly reduced CKD G2	60–89 mL/min
Moderately reduced CKD G3	30–59 mL/min
Severely reduced CKD G4	15–29 mL/min
Kidney failure CKD G5	<15 mL/min

What This Calculator Measures

Calculates creatinine clearance from a 24-hour urine collection using urine creatinine, serum creatinine, and 24-hour urine volume, providing the classic timed-collection estimate of GFR.

How to Use

Use a complete 24-hour collection; incomplete collection underestimates clearance.
Enter urine creatinine, 24-hour urine volume, and serum creatinine.
Review the CrCl and verify collection completeness against expected daily creatinine excretion.

Interpretation Guide

CrCl ≥ 90 mL/min is normal in young adults, 60–89 mildly reduced (CKD G2), 30–59 moderately reduced (CKD G3), 15–29 severely reduced (CKD G4), and < 15 indicates kidney failure (CKD G5). CrCl overestimates true GFR because creatinine is also secreted by tubules, especially at low GFR.

Clinical Significance

The timed 24-hour creatinine clearance remains the classical bedside GFR estimate and a benchmark against which estimating equations are validated, though it requires careful collection.

When to Use

When a timed collection is feasible and estimating equations are unreliable (extremes of body habitus)
Research protocols requiring measured GFR estimates
Verifying drug-dosing estimates in select patients

When Not to Use

When the 24-hour collection is incomplete or serum creatinine is unstable
As a routine replacement for CKD-EPI or Cockcroft-Gault in drug dosing
In acute kidney injury with rapidly changing renal function

Limitations

Collection errors are common and underestimated clearance.
Overestimates true GFR due to tubular creatinine secretion.
Serum creatinine must be stable during the collection.

Worked Example

A 55-year-old man undergoing renal evaluation has a 24-hour urine creatinine of 80 mg/dL in a volume of 1800 mL, with a serum creatinine of 1.0 mg/dL.

Inputs:

urineCreatinine: 80

urineVolume: 1800

serumCreatinine: 1.0

CrCl = (80 × 1800) ÷ (1.0 × 1440) = 100 mL/min. This is a normal creatinine clearance.

Evidence

Source: Classic renal physiology definition
Reference: Levey AS, et al. Expressing the Modification of Diet in Renal Disease Study equation for estimating glomerular filtration rate with standardized serum creatinine values. Clin Chem. 2007;53(4):766-772.
Reviewed By: MedCalcHub Clinical Team
Version: 1.0
Updated: 2026-08

Levey AS, et al. Clin Chem. 2007;53(4):766-772.
Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron. 1976;16(1):31-41.

References

Levey AS, et al. Expressing the Modification of Diet in Renal Disease Study equation for estimating glomerular filtration rate with standardized serum creatinine values. Clin Chem. 2007;53(4):766-772. (Validation Study)
Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron. 1976;16(1):31-41. (Original Description)

Frequently Asked Questions

Why does CrCl overestimate true GFR?

Creatinine is filtered and also actively secreted by proximal tubules, so urinary creatinine clearance exceeds the true filtration rate by roughly 10–20%, with a larger gap at low GFR.

How do I check whether the 24-hour collection was complete?

Compare the collection's total creatinine (urine creatinine × volume) with the expected daily excretion (~15–20 mg/kg/day in men, 10–15 mg/kg/day in women). Wide deviations suggest over- or under-collection.

Disclaimer: This calculator is intended for educational and clinical decision support purposes only. Collection completeness and clinical context are essential when interpreting creatinine clearance.