eGFR (kidney function) blood test: what it measures and what can change it
eGFR estimates how much blood the kidneys filter each minute. It is calculated from creatinine with age and sex, not measured directly.
General information about the test, from Hea's guide and the NHS · Last reviewed 5 November 2026
What it measures, and why GPs check it
eGFR
eGFR estimates how much blood the kidneys filter each minute. It is calculated from creatinine with age and sex, not measured directly.
It is one half of the UK kidney check; the other half is the urine albumin test (ACR).
Urine albumin (ACR)
The urine albumin-to-creatinine ratio shows how much protein leaks into the urine. A first-morning sample is the reliable one.
It picks up kidney damage earlier than blood tests and changes what a GP does next.
Levels in UK guidance
Ranges differ between labs — your report shows your lab's range.
eGFR
- 60 mL/min/1.73m² and above, with no other sign of kidney damage, is usually reported as normal. NICE NG203 table 1; KDIGO 2024
- Below 60 for the first time: NICE asks for a repeat within 2 weeks, because a single low value can be temporary (illness, dehydration, medicines). NICE NG203 1.1.8, 1.3.6
- Chronic kidney disease is only diagnosed when the change lasts at least 3 months, so one result is never the diagnosis. KDIGO 2024; NICE NG203
- Eating meat in the 12 hours before the test can lower the result. NICE NG203 1.1.4
Urine albumin (ACR)
- Below 3 mg/mmol is the normal category (A1). NICE NG203 1.1.12; KDIGO
- 3–70 mg/mmol: NICE asks to confirm it on a first-morning sample; 70 mg/mmol and above needs no repeat and goes to the GP. NICE NG203 1.1.12–1.1.13
- Hard exercise the day before, a urine infection, fever or a period can raise it without kidney disease. Lab Tests Online UK: Urine albumin to creatinine ratio; KDIGO 2024 Clinical Practice Guideline for CKD (PMID 38490803), table 16
What can shift the number
Before the test
- Ate meat in the 12 hours before. Meat eaten in the 12 hours before can raise creatinine and lower eGFR for some hours: NICE advises not eating meat in the 12 hours before an eGFR test. NICE NG203 Chronic kidney disease: assessment and management (2021), rec 1.1.4; Lab Tests Online UK: Creatinine; eGFR
- Hard exercise or cycling in the week before. Hard exercise can raise the urine albumin ratio for a short time without kidney disease. Lab Tests Online UK: Urine albumin to creatinine ratio; KDIGO 2024 Clinical Practice Guideline for CKD (PMID 38490803), table 16
- Vomiting or diarrhoea, a fever, or very little to drink in the week before. Being short of fluid or a short illness can raise creatinine and urea and lower eGFR for a while; vomiting and diarrhoea can lower sodium and potassium. Lab Tests Online UK: Creatinine; eGFR; Urea; Sodium; Potassium; NICE NG148 Acute kidney injury (2019, updated 2024), recs 1.1.1, 1.1.10; NICE NG203 (2021), rec 1.1.8
Now or in the last 3 months
- Pregnant. In pregnancy the usual ranges for many tests are different: show these results to your midwife or GP. NICE NG201 Antenatal care (2021); NICE NG3 Diabetes in pregnancy (2015, updated 2020); RCOG Green-top Guideline 76: thyroid disorders in pregnancy (2025; PMID 40240075); NICE NG239 (2024) rec 1.3.2; BSG guidelines on the management of abnormal liver blood tests (2018); Lab Tests Online UK: Lipid profile; C-reactive protein (CRP); ESR
Some medicines and supplements can change this result too. When you add your results, Hea asks which ones you take.
What a GP reads it with
eGFR
Read together with: Urine albumin (ACR), Creatinine. NICE NG203 Chronic kidney disease: assessment and management (2021), rec 1.2.1
A GP usually repeats it with a urine ACR, checks blood pressure and reviews medicines that affect the kidneys.
Urine albumin (ACR)
Read together with: eGFR. NICE NG203 (2021), rec 1.2.1
A GP usually asks for a first-morning repeat, checks blood pressure and eGFR, and reviews medicines.
Questions to ask your GP
- Should this be repeated, and with a urine test?
- Do any of my medicines affect this number?
- What was my previous result, if the practice has one?
- Was this a first-morning sample?
- Could something temporary explain it?
Safety first
If your lab or GP has flagged your result as urgent, follow their advice first.
Not for emergencies: call 999 or NHS 111.
Questions people ask
What is eGFR in a blood test?
eGFR stands for estimated glomerular filtration rate. It is worked out from the level of creatinine, a waste product, in your blood, together with your age, size and sex. It estimates how much your kidneys filter each minute. A urine test called ACR is also done to give a fuller picture.
NHS: Chronic kidney disease – Diagnosis, Page last reviewed 22 March 2023Does one low eGFR result mean kidney disease?
No, one result is not enough. When an adult's first eGFR is below 60, NICE asks for a repeat within 2 weeks and a urine ACR test. Chronic kidney disease is only diagnosed when a change lasts more than 3 months, for example an eGFR below 60 on tests at least 90 days apart.
NICE NG203: Chronic kidney disease: assessment and management, Last updated 24 November 2021Do I need to avoid anything before an eGFR blood test?
Yes. NICE advises adults not to eat any meat in the 12 hours before a blood test for eGFR. NICE also asks for the sample to reach the laboratory and be processed within 12 hours.
NICE NG203: Chronic kidney disease: assessment and management, Last updated 24 November 2021What can make an eGFR result less accurate?
NICE says eGFR can be less reliable in pregnancy, after a sudden kidney injury, with fluid swelling, and in people with a lot of muscle or with muscle-wasting conditions. Using protein supplements, being malnourished or having had an amputation can affect it too. It has also not been well tested in some ethnic groups living in the UK.
NICE NG203: Chronic kidney disease: assessment and management, Last updated 24 November 2021What can I do to look after my kidneys?
For people with kidney disease, the NHS recommends not smoking, a healthy, balanced diet with less salt, regular exercise and keeping alcohol within the recommended limit. It also advises losing weight if you are overweight and keeping blood pressure under control. Ask your GP or pharmacist before taking over-the-counter anti-inflammatory painkillers.
NHS: Chronic kidney disease – Treatment, Page last reviewed 22 March 2023Got your result? Start with this question in your AI.
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Related
Sources
Each line about the test above names the guideline it comes from, as Hea's guide cites it. The answers to the questions come from:
- NHS: Chronic kidney disease – Diagnosis, Page last reviewed 22 March 2023
- NICE NG203: Chronic kidney disease: assessment and management, Last updated 24 November 2021
- NHS: Chronic kidney disease – Treatment, Page last reviewed 22 March 2023