Creatinine
Also known as: Serum creatinine, Cr
Creatinine is a waste product made by your muscles as they use energy. Your kidneys filter it out of your blood, so the amount in your blood gives an indirect sense of how your kidneys are filtering.
Why it's measured
Creatinine is a routine part of metabolic panels and is used along with other values to look at kidney function. It can be influenced by muscle mass, hydration, and certain foods.
Typical range
Reference ranges vary by lab and can differ with sex and body size. Because muscle mass and hydration affect creatinine, doctors often pair it with the eGFR calculation.
What high values can mean
A higher creatinine is one marker doctors examine when looking at kidney filtering, usually together with eGFR and your history rather than alone.
What low values can mean
A lower creatinine can relate to factors like lower muscle mass and is usually interpreted in context by your doctor.
Questions to ask your doctor
- What does my creatinine, together with my eGFR, suggest about my kidneys?
- Could hydration or muscle mass have influenced this?
- Should this be rechecked, and when?
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Try the explainerEducational information only — not medical advice, diagnosis, or treatment. Reference ranges vary by lab; always use your own lab's range and discuss results with a qualified clinician.