Creatinine
A muscle waste product used to estimate how well the kidneys filter blood.
| Typical reference range (male) | 0.76–1.27 mg/dL |
| Typical reference range (female) | 0.57–1 mg/dL |
Ranges vary by laboratory, method, age and sex: always use the range printed on your own report. Why labs differ.
What it measures
Creatinine is produced at a fairly steady rate from creatine phosphate in muscle and is cleared almost entirely by kidney filtration. When filtration falls, blood creatinine rises.
Why it matters
Serum creatinine is the standard input for eGFR, the main screening measure for chronic kidney disease. Changes over time are often more informative than a single value.
What a high result can mean
Elevated values can mean reduced kidney function, dehydration or urinary obstruction, but also high muscle mass, creatine supplements, heavy exercise in the prior day or two, or a large cooked-meat meal. Some drugs (trimethoprim, cimetidine, certain HIV drugs) block creatinine secretion without harming the kidneys.
What a low result can mean
Low creatinine usually reflects low muscle mass (older age, frailty, small body size), pregnancy or severe liver disease; it can make eGFR overestimate kidney function.
What affects the result
Avoid creatine supplements, intense exercise and large meat meals 24-48 hours before testing for the most accurate value. Muscular people may appear to have reduced eGFR; cystatin C can clarify. Watch the trend and urine albumin/creatinine ratio.
Units and conversion
Usually reported in mg/dL.
- From umol/L: multiply by 0.011 to get mg/dL
- From mmol/L: multiply by 11.31 to get mg/dL
Also called on lab reports
Creatinine, Serum, Serum Creatinine, Creat, Creatinine, Blood
Related tests: Kidney Function
This page is educational and does not replace advice from a healthcare professional.