Checks creatinine, eGFR, sodium and urea — the standard markers used to assess how well the kidneys are working.
About this test
Kidney Function Tests measure creatinine, estimated glomerular filtration rate, sodium, and urea. These markers help provide information about how the kidneys filter waste and maintain fluid and mineral balance. The test may be useful as part of a general health check or when monitoring medication or a known kidney concern. It can help identify results that need further investigation, but one abnormal result does not always mean permanent kidney disease. Hydration, muscle mass, medication, and recent illness can affect some results. No special preparation is usually required unless advised.
What’s included4 markers
- Creatinine
- eGFR
- Sodium
- Urea
What to expect
Before your test
Drink plenty of water beforehand. It makes the blood draw easier.
Some tests need you to fast for at least 12 hours, with water only. If you're not sure about yours, ask us before your appointment.
Stop oral and IV vitamin supplements 24 hours before your test, as they can affect some results. Keep taking your regular prescribed medication unless your GP tells you otherwise. Some types of hormonal contraception can affect results, so mention it to us.
At your appointment
You'll fill in a short medical questionnaire first. We'll also check your blood pressure, heart rate and blood oxygen level. A healthcare professional then takes your sample from a vein at our clinic. The visit takes about 15 minutes.
A cold numbing spray is available if you'd like one. If you feel nervous, tell us and we'll help you feel at ease.
Your results
Results usually take 3 to 7 working days. We can't guarantee this, because some things are outside our control. A doctor reviews your results and adds recommendations to your report. We email the report to you as a PDF.
If there's a problem with your sample, we may ask you to come back for another blood draw.
After your test
You don't need any recovery time. Keep the dressing on for 30 minutes and keep it clean and dry.
Who can have a blood test?
Blood tests are for people aged 18 and over. You don't need a GP referral letter. Please book tests for yourself only.
Appointments are available Monday to Saturday.
Are the laboratories accredited?
Your sample is analysed in a laboratory that is CQC-registered and accredited by UKAS.
A blood test gives you information. It isn't a diagnosis. If you have symptoms or you're worried about your health, speak to your GP.