What is creatinine and what does it tell you?
Creatinine is a muscle-derived metabolite filtered by the kidneys. It is the primary input to eGFR. Muscular adults have higher baseline creatinine without worse kidney function.
Full answer
Creatinine is produced continuously by muscle metabolism and cleared almost exclusively by the kidneys. Serum creatinine is the workhorse input to most eGFR equations. The interpretive nuance: muscle mass strongly influences the value. A muscular adult and a frail adult with the same eGFR have very different prognoses. Very low creatinine usually reflects low muscle mass, not exceptional kidney function. oMeds provider review interprets creatinine with body composition context and prioritizes trend over any single value. Acute creatinine rises occur with dehydration, NSAIDs, ACEi/ARB initiation, and intense muscle injury.
Educational. Not a substitute for individualized provider review.
- Creatinine — Primary source · oMeds
- Reviewed by Dr. Laura Purdy, MD, MBA · Clinical Director, oMeds · Last reviewed 2026-05-29