Kidney / U&E
Creatinine & eGFR blood test
A creatinine blood test measures a waste product your muscles produce and your kidneys clear, and it is used to check how well your kidneys are working. From your creatinine, your age and your sex, the lab calculates your eGFR (estimated glomerular filtration rate), a score of kidney function out of roughly 100 that is usually the number people are given.
- What it measures
- Kidney function (creatinine, and the eGFR from it)
- Sample
- Venous blood sample
- Fasting
- Not required
- Also known as
- eGFR, estimated glomerular filtration rate, kidney function
- Included in 57 Health tests
- 8 panels, from £95
Creatinine & eGFR reference range
Guide only| Category | Guide range |
|---|---|
| Normal kidney function (G1) | 90 or above mL/min/1.73m² |
| Mildly reduced (G2) | 60–89 mL/min/1.73m² |
| Mild to moderate (G3a) | 45–59 mL/min/1.73m² |
| Moderate to severe (G3b) | 30–44 mL/min/1.73m² |
| Severely reduced (G4) | 15–29 mL/min/1.73m² |
| Kidney failure (G5) | below 15 mL/min/1.73m² |
These eGFR bands are the standard UK CKD stages. An eGFR in the G1 or G2 band is only labelled as chronic kidney disease if there are other signs of kidney damage that persist for at least three months, so a single mildly low reading is not a diagnosis. Creatinine itself depends on muscle, so a general adult guide is roughly 59–104 µmol/L in women and 64–110 µmol/L in men, with your report's own range taking precedence.
These are general UK adult guide ranges from public health sources, shown for orientation only. Reference ranges vary by laboratory, assay, age and sex, so your result is always interpreted against the range quoted by the analysing laboratory on your report.
What does a high creatinine level mean?
A high creatinine, which shows up as a low eGFR, suggests your kidneys are clearing waste less efficiently than expected. Causes range from dehydration and a short-term illness to longer-term chronic kidney disease, and some medicines and a very high protein or creatine intake can nudge it up too.
One raised reading is not a diagnosis. Because creatinine reflects muscle as well as kidney function, it runs naturally higher in very muscular people, and a temporary rise often settles. A genuinely reduced eGFR is confirmed on a repeat test, usually a few weeks later, and read alongside a urine check for protein.
What does a low creatinine level mean?
A low creatinine, giving a high eGFR, is usually normal and not a concern. It most often reflects lower muscle mass, so it can be seen in people who are slighter, older or less muscular, and during pregnancy.
Rarely, a persistently low creatinine goes with significant muscle loss or undernutrition, so it is considered alongside the rest of your results rather than on its own.
When to consider a creatinine test
- Diabetes or high blood pressure, which affect the kidneys
- A family history of kidney disease
- Taking medicines that need kidney monitoring
- A general health or U&E check
- Before and during some treatments
- Swelling, or a change in how often you pass urine
Frequently asked questions
This page is general information about a blood marker and is not medical advice or a diagnosis. A creatinine test screens and gives context; results are interpreted by a clinician alongside your symptoms, history and other markers. Always follow the guidance on your own report.