Creatinine & eGFR
Also known as: Serum creatinine, Kidney function test, GFR, eGFR CKD-EPI
Creatinine is a waste product filtered by the kidneys; eGFR (estimated glomerular filtration rate) converts it into a percentage of normal kidney function. Together they are the primary tools for detecting and staging chronic kidney disease.
Venous blood (serum separator tube)
2–4 hours
Not required
Kidney Function
Reference Ranges
| Measurement | Reference Range | Unit |
|---|---|---|
| Creatinine (men) | 0.74 – 1.35 | mg/dL |
| Creatinine (women) | 0.59 – 1.04 | mg/dL |
| eGFR (normal) | ≥ 90 | mL/min/1.73m² |
| eGFR CKD stage 2 | 60 – 89 | mL/min/1.73m² |
| eGFR CKD stage 3a | 45 – 59 | mL/min/1.73m² |
| eGFR CKD stage 3b | 30 – 44 | mL/min/1.73m² |
| eGFR CKD stage 4 | 15 – 29 | mL/min/1.73m² |
| eGFR CKD stage 5 (kidney failure) | ≤ 15 | mL/min/1.73m² |
Reference ranges are typical adult values. Your laboratory may use slightly different intervals — always use your lab's reported reference.
What This Test Measures
Creatinine is produced at a constant rate by muscle metabolism and filtered freely by the kidneys without reabsorption. When filtration declines, creatinine accumulates. The CKD-EPI equation converts creatinine into eGFR using age, sex, and creatinine — giving a standardised percentage of normal kidney function that is comparable across patients of different body sizes.
When Is This Test Ordered?
- Routine kidney function check in adults
- Monitoring diabetic and hypertensive nephropathy
- Dose adjustment for renally cleared medications (metformin, NSAIDs, antibiotics)
- Evaluating acute kidney injury in hospitalised patients
- Pre-contrast imaging studies
When Results Are High
High creatinine and low eGFR indicate reduced kidney filtration. The cause can be pre-renal (dehydration), renal (nephropathy, glomerulonephritis), or post-renal (obstruction). A sudden rise in creatinine above 50% of baseline is acute kidney injury and warrants urgent evaluation.
When Results Are Low
Low creatinine is generally not clinically significant — it reflects low muscle mass (elderly, frail, or muscle-wasting conditions). Very low creatinine can make eGFR unreliable (overestimates true GFR in severely sarcopenic patients).
CKD staging and clinical implications
| eGFR Stage | eGFR (mL/min) | Clinical Implications |
|---|---|---|
| G1 | ≥ 90 | Normal or high; monitor if albuminuria present |
| G2 | 60–89 | Mildly reduced; address cardiovascular risk |
| G3a | 45–59 | Mild–moderate; restrict NSAIDs, adjust drug doses |
| G3b | 30–44 | Moderate–severe; nephrology referral recommended |
| G4 | 15–29 | Severe; prepare for renal replacement therapy |
| G5 | < 15 | Kidney failure; dialysis or transplant planning |
Factors That Can Affect Your Result
- Muscle mass is the main determinant — bodybuilders have higher creatinine without kidney disease
- Creatine supplementation raises creatinine transiently
- Cooked meat raises creatinine for several hours after eating
- eGFR is less accurate at extremes of muscle mass (very low or very high)
- Cimetidine blocks tubular creatinine secretion, raising serum creatinine without affecting true GFR
Tracking This Test Over Time
Kidney function declines slowly in chronic disease — a drop in eGFR of 5 mL/min/1.73m² per year is clinically significant even when both values stay within a normal-appearing range. Tracking eGFR over years is far more informative than any single test.
Track your Creatinine / eGFR in LoomsRelated Tests
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Medical disclaimer
This page is for educational purposes only and does not constitute medical advice. Reference ranges vary between laboratories, and results must be interpreted in the context of your symptoms, history, and other tests. Always discuss your results with your healthcare provider. Content reviewed by the Looms medical team, 2026-06-01.