What does the Creatinine, Serum test measure?

Why is Creatinine, Serum measured?

Serum creatinine within the CMP provides the raw substrate for eGFR calculation and a cross-check on eGFR reliability. Elevated creatinine with reduced eGFR confirms impaired glomerular filtration; it also screens for acute kidney injury (AKI) in hospitalised patients when compared against prior baseline. Isolated creatinine elevation without eGFR reduction may reflect increased muscle mass (athletes, bodybuilders) or high dietary meat intake rather than renal impairment. Creatinine is also elevated by certain medications including trimethoprim and cimetidine (which inhibit tubular creatinine secretion) without affecting true GFR — a clinically important drug-laboratory interaction to recognise.

Reference ranges

Standard reference

Male: 0.70–1.30 mg/dL (61.9–114.9 µmol/L); Female: 0.50–1.10 mg/dL (44.2–97.2 µmol/L) # REVIEWER FLAG: Confirm Quest Diagnostics sex-specific creatinine reference ranges — female upper limits typically range from 0.9–1.1 mg/dL depending on the platform; confirm Quest's specific values. Note that creatinine reference ranges derived from mixed-sex populations historically overestimate the female upper limit, which is now increasingly recognised as approximately 0.9 mg/dL in women.

Functional medicine optimal

Male: 0.80–1.10 mg/dL; Female: 0.60–0.90 mg/dL (functional medicine optimal reflecting adequate muscle mass and normal glomerular filtration without early subclinical impairment). # REVIEWER FLAG: Not a standardised clinical guideline target — reviewer to confirm framing.

Units

mg/dL, µmol/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.