Kidneys, electrolytes and minerals
EGFR blood test: what a high or low result means
What eGFR means on your blood test, why it might be low, and what to ask your doctor about your kidney function.
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Explain my results → Available on web, iOS & Android.What is eGFR?
eGFR stands for estimated glomerular filtration rate. It is an estimate of how well your kidneys are filtering waste out of your blood. It is not measured directly; it is calculated from your blood creatinine level, age and sex (current UK and US formulas no longer adjust for ethnicity). A higher eGFR generally means better kidney function. It is usually reported with a kidney blood test called U&E (urea and electrolytes), or a basic or comprehensive metabolic panel in the US.
Why is this test done?
- To check kidney function as part of a routine blood test
- To monitor long-term conditions that affect the kidneys, such as diabetes and high blood pressure
- To check that medicines are safe, as some are cleared by the kidneys
- To follow up chronic kidney disease
What does a high eGFR mean?
A high eGFR is usually not a concern. It can be seen in younger people, during pregnancy, and sometimes early in diabetes. Labs often report eGFR above a certain level simply as greater than that value.
Possible reasons include:
- Younger age
- Pregnancy
- Low muscle mass, which lowers creatinine and so raises the calculated eGFR
What does a low eGFR mean?
A low eGFR can mean your kidneys are not filtering as well as usual. A single low result is not enough to diagnose kidney disease; doctors look for a result that stays low over at least three months.
Possible reasons include:
- Chronic kidney disease, often linked to diabetes or high blood pressure
- Dehydration or a recent illness
- Some medicines, such as anti-inflammatory painkillers
- Older age, as kidney function naturally declines with age
- High muscle mass or eating a lot of meat before the test, which raises creatinine and lowers the calculated eGFR
Why we don't list a "normal range". Reference ranges differ between laboratories and can depend on your age, sex and whether you are pregnant. The range printed next to your result on your own report is the one that applies to you, so use that, and talk to your doctor about what your result means for you.
What can affect your eGFR result?
- Dehydration
- Eating cooked meat in the hours before the test
- Hard exercise shortly before the test
- Muscle mass, as eGFR is less accurate in very muscular or very frail people
- Pregnancy
Make sense of the whole report, not just one line
Results are easier to understand together. Patiently AI explains your report as a whole and writes personalised questions for your next appointment.
Try it with your own results → Paste, upload or photograph your results.Questions to ask your doctor
- Is my eGFR stable, or has it changed compared with before?
- Do I have chronic kidney disease, and if so, what stage?
- Should my urine be checked for protein (ACR)?
- Do any of my medicines need to be changed because of my kidney function?
- What can I do to protect my kidneys?
Frequently asked questions
Is a low eGFR serious?
It depends on how low it is and whether it stays low. A slightly low result after dehydration or illness often improves. Doctors diagnose chronic kidney disease only when eGFR stays low, or there are other signs of kidney damage, for at least three months.
Why is eGFR an estimate?
Measuring kidney filtration directly is complicated, so labs estimate it from creatinine in your blood using a formula. That is why things that change creatinine, such as muscle mass or a meat-heavy meal, can affect your eGFR.
What is the difference between eGFR and creatinine?
Creatinine is the waste product actually measured in your blood. eGFR is calculated from creatinine to estimate kidney function. When creatinine goes up, eGFR goes down.
Can Patiently AI explain my eGFR result?
Yes. Paste your results, or upload a photo, PDF or Word file, and Patiently AI explains them in plain English, sticking to the numbers and ranges on your own report rather than adding its own, and suggests questions to ask your doctor. It is free, needs no account, and removes identifying details on your device first.