Kidney Function Blood Test: eGFR Guide
Your kidneys work around the clock, filtering waste products from your blood, balancing your body’s fluids, and regulating blood pressure. But unlike a headache or a chesty cough, kidney problems rarely announce themselves with obvious symptoms. That’s why a kidney function blood test is one of the most important checks you can have, especially as you get older.
In this guide, we’ll cover what kidney function blood tests measure, what the results mean, and how to get tested privately in the UK.
What is a kidney function blood test?
A kidney function blood test measures how well your kidneys are filtering waste products from your blood. The two main markers are creatinine and eGFR.
Creatinine is a waste product produced by your muscles during normal wear and tear. Healthy kidneys filter creatinine out of your blood and into your urine. If your creatinine level is high, it can mean your kidneys aren’t filtering as well as they should.
eGFR (estimated Glomerular Filtration Rate) is calculated from your creatinine level, taking into account your age, sex, and sometimes your ethnicity. It estimates how many millilitres of blood your kidneys can filter per minute. A normal eGFR is above 90 mL/min, though values between 60 and 89 can be considered normal if there’s no other evidence of kidney disease.
Many kidney function panels also include urea (another waste product from protein breakdown) and uric acid (a breakdown product of purines found in certain foods).
Why would you need a kidney function test?
You might consider a kidney function blood test if you are over 40 (kidney function naturally declines with age), have high blood pressure or diabetes, or have a family history of kidney disease. Hypertension is a leading cause of kidney damage, and high blood sugar can damage the tiny blood vessels in your kidneys.
Other reasons to test: you take long-term medications that can affect the kidneys, such as NSAIDs (ibuprofen, naproxen) or certain blood pressure medications; you experience symptoms like swollen ankles, persistent tiredness, changes in urination, or lower back pain; or you simply want a baseline, because knowing your kidney function when you’re healthy helps spot changes later.
The NHS offers kidney function tests as part of routine health checks, but if you want to track your kidney health more regularly or don’t qualify for NHS testing, private blood tests are a convenient option.
What do the results mean?
Your kidney function test results typically include:
| Marker | What It Measures | Typical Normal Range |
|---|---|---|
| eGFR | How well kidneys filter waste | Above 90 mL/min (60–89 borderline) |
| Creatinine | Waste from muscle breakdown | 60–110 μmol/L (varies by muscle mass) |
| Urea | Waste from protein breakdown | 2.5–7.8 mmol/L |
| Uric Acid | Waste from purine breakdown | 150–480 μmol/L |
eGFR stages of chronic kidney disease (CKD):
| Stage | eGFR |
|---|---|
| Stage 1 | Above 90 (normal kidney function) |
| Stage 2 | 60–89 (mildly reduced) |
| Stage 3 | 30–59 (moderately reduced) |
| Stage 4 | 15–29 (severely reduced) |
| Stage 5 | Below 15 (kidney failure) |
It’s important to remember that a single out-of-range result doesn’t necessarily mean you have kidney disease. Dehydration, a high-protein meal before the test, or intense exercise can temporarily raise creatinine levels. Your GP will look at trends over time, not just one-off readings.
Private kidney function blood tests in the UK
Several UK providers offer kidney function testing as a standalone test or as part of a broader health panel. Here are the most affordable options:
To compare kidney function test prices across all providers side by side, visit our compare page to look at kidney function or liver and kidney tests.
| Provider | Test Name | Price | Link |
|---|---|---|---|
| Medichecks | Kidney Check Blood Test | £39 | View test |
| Forth | Kidney Function Blood Test | £49 | View test |
| Bluecrest | Advanced Biochemistry Profile | £90 | View test |
| Randox | General Health Test | £84 | View test |
| Thriva | General Health Blood Test | £105.30 | View test |
| Numan | Full Check-up / Core Blood Test | £88 | View test |
Medichecks offers the most affordable dedicated kidney check at just £39, while Forth’s kidney function test comes in at £49. If you want a broader health overview that includes kidney markers alongside other important checks, the larger health MOTs from Bluecrest, Randox, and Thriva are excellent value.
How kidney function tests fit into your wider health
Your kidneys don’t work in isolation. They’re closely linked to your heart, liver, and metabolic health, which is why many comprehensive health panels bundle kidney markers with other useful checks. If you’re getting a kidney function test, consider adding a cholesterol or diabetes (HbA1c) test at the same time. Many providers offer finger-prick collection that tests multiple markers from a single sample.
What if your results are abnormal?
If your kidney function test comes back with concerns, here’s what you can do:
Stay hydrated. Even mild dehydration can raise creatinine levels. Aim for 6–8 glasses of water a day, more if you exercise or it’s hot.
Reduce salt intake. Too much salt raises blood pressure, which puts strain on your kidneys. The NHS recommends no more than 6g of salt per day.
Watch your protein intake. Very high protein diets can increase the workload on your kidneys. If you already have reduced kidney function, your GP may advise moderating protein.
Limit NSAIDs. Medications like ibuprofen and naproxen can reduce blood flow to the kidneys. Use them sparingly and speak to your GP if you need long-term pain relief.
Manage blood pressure and blood sugar. If you have high blood pressure or diabetes, keeping these under control is the single best thing you can do for your kidney health.
Don’t smoke. Smoking narrows blood vessels, including those in the kidneys, reducing their ability to filter blood.
Get regular checks. If your eGFR is below 60, your GP will typically recommend repeat testing every 3–12 months to monitor trends.
Summary
Kidney function blood tests are a simple but powerful way to check in on two of your body’s most important organs. Whether you have a known risk factor like diabetes or high blood pressure, or you just want a baseline to compare against in future years, a private kidney function test is quick, affordable, and easy to arrange from home. At prices starting from £39, there’s little reason to wait for symptoms, because by the time kidney problems make themselves known, they’re often further along than they need to be. A thirty-second finger prick today could save you a lot of worry tomorrow.
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