What it measures
- Creatinine
- eGFR
- Urea
- Sodium
- Potassium
- Chloride
- Calcium
- Phosphate
Who it’s for
- High blood pressure or diabetes, the two biggest causes of kidney disease
- Regular use of anti-inflammatory painkillers such as ibuprofen
- Medicines that need kidney monitoring
- Swollen ankles, tiredness or changes in how often you pass urine
- A family history of kidney disease
What’s measured
Creatinine is a waste product from your muscles that healthy kidneys clear steadily. From your creatinine, age and sex, your eGFR (estimated glomerular filtration rate) is calculated: the main measure of how well your kidneys filter. Urea is another waste product. Sodium, potassium and chloride are electrolytes that keep your nerves, muscles and heart working properly, and calcium and phosphate are minerals your kidneys help to balance.
Things that can affect your result
A large meat meal, creatine supplements or very hard exercise in the day before can push creatinine up a little and make eGFR look lower. Dehydration can raise urea. If a result is borderline, a repeat test usually makes things clear.
| eGFR (mL/min/1.73m²) | What it usually means |
|---|---|
| 90 or above | Normal kidney filtration |
| 60 to 89 | Mildly reduced: often normal with age if there are no other signs of kidney damage |
| Below 60 for 3 months or more | Suggests chronic kidney disease |
How to prepare
- Drink a couple of glasses of water beforehand: it makes the sample quicker and easier to take.
- No fasting needed. Eat and drink as normal.
- Avoid a large meat meal and very intense exercise in the 24 hours before.
- Mention creatine supplements if you take them, as they can raise creatinine.
How it works at our Croydon clinic
Book online
Choose your test and a time that suits you. No GP referral needed.
A 15-minute visit
A trained clinician takes a small blood sample at 169 Shirley Road, Croydon. Tell us if you’re nervous.
Results in 1–3 days
A clear report showing each result against its reference range.
Next steps
Share your report with your GP, who can arrange NHS follow-up if anything needs it.
Questions
What is a normal eGFR?
90 or above is normal. 60 to 89 can be normal, especially as you get older, if there are no other signs of kidney damage. Below 60 on tests at least three months apart suggests chronic kidney disease.
Does this test check for kidney stones?
No. Kidney stones are usually found with a scan. This test shows how well your kidneys are working.
How much is a Kidney Function Test in Croydon?
£70 at our clinic at 169 Shirley Road, Croydon, including taking your blood sample and your report.
How quickly will I get my results?
Usually within 1 to 3 days, in a clear report showing each result against its reference range.