What it measures
Creatinine is a waste product made by muscles as they work. The kidneys clear it from the blood, so the level in the blood is used to check how well the kidneys are filtering. It is the basis of the eGFR result.
Why people test it
- Part of a kidney function test, often checked every year with diabetes or high blood pressure.
- Monitored on medicines that can affect the kidneys, such as some blood pressure medicines and lithium.
- Used to work out eGFR, the estimate of how much blood the kidneys filter.
- Creatine supplements raise creatinine, which can make kidney results look worse than they are.
- More muscle means more creatinine, so very muscular people often read higher.
- Hard training or a large meat meal shortly before the test can also raise it.
Typical range
Ranges vary between labs, with the method used, age and sex, and your report shows the lab's own range. One NHS trust lab gives 64 to 104 µmol/L for adult men and 49 to 90 µmol/L for adult women. Source: Oxford University Hospitals NHS Foundation Trust: biochemistry reference ranges.
Finger-prick or vein?
A finger-prick sample is usually fine for creatinine. A vein draw works too and is used when it is part of a larger panel.
Creatine raises creatinine, which can make kidney results look worse than they are. Cystatin C gives a truer read.
