Creatinine
A muscle waste product the kidneys filter out.
What it measures
The concentration of creatinine, a waste product produced by normal muscle metabolism and removed from the blood by the kidneys.
Why a doctor orders it
It is the standard measure used to assess kidney filtering, and is followed over time in people with kidney disease, diabetes, or high blood pressure, and before and during medications processed by the kidneys.
What is generally associated with a higher result
Broadly associated with reduced kidney filtering from any cause, with dehydration, with high muscle mass, with a high-meat meal shortly before the draw, and with certain medications that alter how creatinine is handled without changing kidney function itself.
What is generally associated with a lower result
Broadly associated with low muscle mass, older age, pregnancy, and prolonged illness.
Everyday things that move this number
Not every shift in a value reflects disease. These are ordinary factors known to affect this particular measurement:
- Muscle mass - a very muscular person runs higher without any kidney problem
- Hydration
- A large meat meal before the draw
- Creatine supplements
Questions to take to your appointment
- What is my eGFR, and how does it compare to last time?
- Do any of my medications need dose adjustment based on this?
Build a printable questionnaire with your own results →
Where to read more
MedlinePlus, from the US National Library of Medicine, publishes patient-facing pages on individual lab tests and is a reliable next stop: medlineplus.gov/lab-tests .
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