Health & Fitness · 肌酐（Creatinine） · Updated 2026-10-25
What Is Creatinine?
Definition
Creatinine comes from irreversible breakdown of muscle phosphocreatine, produced in proportion to muscle mass at a stable daily rate and almost entirely filtered by the glomeruli — making serum creatinine a lagging alarm for kidney filtration. Typical ranges: men 54-106 μmol/L, women 44-97 μmol/L (varies by lab). The key flaw: kidney reserve is huge, and creatinine rises visibly only after half the filtration is gone — so check eGFR (estimated from creatinine, age and sex): above 90 normal, below 60 warrants follow-up.
Formula
eGFR (CKD-EPI) ≈ f(serum creatinine, age, sex); normal ≥ 90 mL/min/1.73m²
Worked Example
A 45-year-old man with creatinine 98 μmol/L ("normal" on paper) has a CKD-EPI eGFR of only 78 — stage G2 mild decline warranting repeat urine albumin checks plus blood pressure and glucose control.
Common Misconception
"Normal creatinine means healthy kidneys" — compensation keeps it normal well into decline; eGFR is the sensitive marker. Conversely, high creatinine in gym-goers (large muscle mass, high protein, hard training) is often physiological when mildly elevated (within 20% of the cap) with a normal eGFR.
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