What is eGFR on a blood test?
eGFR estimates how much blood your kidneys filter per minute.
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The short answer
eGFR estimates how much blood your kidneys filter per minute. It isn't measured directly: it's calculated from your creatinine along with your age and sex. That matters, because anything that raises your creatinine lowers your eGFR on paper whether or not your kidneys have changed. At Epicentre it's reported with creatinine at R70.
What does eGFR measure?
Your kidneys filter waste out of your blood. The glomerular filtration rate is how fast they do it, and measuring it directly is slow and awkward, so in practice it's estimated.
The estimate uses creatinine, a waste product your kidneys clear, on the reasonable assumption that if creatinine is piling up, less filtering is happening. Your age and sex are added because muscle mass differs, and muscle is where creatinine comes from.
So eGFR is not a measurement. It's an inference from one number, and it inherits everything that affects that number.
What does a high or low eGFR mean?
Before reading anything into either, remember how reference ranges work. They're built so that 95% of healthy people fall inside them, which means roughly 1 in 20 perfectly normal results sits outside by definition. A single flagged value in an otherwise normal panel is common, and the pattern across related markers matters far more than any one number.
Not sure whether you need this on its own or as part of a panel? Tell us what you're trying to find out.
Ask us on WhatsAppSee all 102 markersWhat else affects eGFR?
These are the things that move the number without anything being wrong, and they're worth knowing before you worry about a result.
- Creatine supplements
- The big one. Creatine breaks down into creatinine, so supplementing raises it by roughly 10 to 30% and drops eGFR on paper while filtration is unchanged. Cystatin C at R694 is the marker that isn't affected.
- Muscle mass
- More muscle means more creatinine at baseline. A heavily muscled person can have a lower eGFR without anything being wrong.
- A heavy protein meal or hard training
- Both raise creatinine briefly. Worth avoiding in the day or two before testing.
- Dehydration
- Concentrates everything in your blood, creatinine included.
The functional view
A standard range answers whether your filtration has fallen far enough to be called disease. A functional reading looks at the direction of travel instead.
Kidney function declines gradually with age in almost everyone, and the standard bands are wide enough that a real, steady decline can happen entirely inside them. One eGFR tells you very little. Three, taken a year apart, tell you a great deal.
This is also the marker where the functional view is most useful about what not to conclude, because a low eGFR in a muscular person taking creatine is usually a measurement artefact rather than a kidney finding.
Where this marker sits in the bigger picture
Assimilation and elimination
What gets taken in and what gets cleared out. Filtration is the elimination half of that, which is why it is watched over years rather than judged on one reading.
This is the thinking behind the functional health report that comes with every blood order at Epicentre. It places each marker on a scale that shows the optimal band as well as the standard range, ranks what needs attention, and compares each result to your last one. Two people with the same "normal" can get very different reports.
Worth being clear about the limits, though. Functional optimal ranges are educational reference recommendations rather than diagnostic thresholds, they are not universally agreed, and a value inside a standard laboratory range is not a disease. What the functional view offers is a direction and a conversation, not a verdict. Both readings of your result are useful, and the standard one is still the one your doctor works from.
Which markers is it read with?
Urea R70 and the full U&E with creatinine at R380. If you supplement or lift, Cystatin C at R694 gives a filtration estimate that muscle and creatine don't distort.
eGFR test
R70Walk in at any branch, no appointment and no doctor's referral if you're paying cash. Results in 2 to 5 working days, and every blood order comes back with a functional health report that puts each marker on a plain-English scale at no extra cost.
See it on the test list Ask us on WhatsAppWhich packages include eGFR and creatinine?
Creatinine, and therefore eGFR, appears on 20 panels. These are the common starting points.
The standard kidney panel.
See what's included →R902Medication Safety and Organ FunctionIncludes egfr and creatinine.
See what's included →R1,409Comprehensive Metabolic Panel (CMP)The broad organ-function panel.
See what's included →R1,562HIV Treatment MonitoringIncludes egfr and creatinine.
See what's included →R1,945Nutritional Status Follow-UpIncludes egfr and creatinine.
See what's included →R2,181Men's Annual FoundationIncludes egfr and creatinine.
See what's included →Plus 14 more panels that include egfr and creatinine. See all packages or tick your own on the pricelist.
Worth reading next
Where can I test eGFR in South Africa?
All three are open Monday to Friday, 08:30 to 16:00, and closed on public holidays. Medical aid rates are roughly 20% higher than the cash rate and generally need a doctor's request with an ICD-10 code.
Basically
eGFR is R70 at Epicentre and you don't need a referral for it. One result slightly outside the range is common and usually means very little on its own. What matters is the pattern with the markers it's read alongside, and whether it has changed since last time.
Frequently asked questions
What is a normal eGFR?
Above 90 is generally treated as normal, 60 to 89 as mildly decreased and below 60 as warranting investigation if it persists. Those bands are guides rather than diagnoses, and a single low reading is usually repeated before anything is concluded.
Why is my eGFR low when I feel fine?
Often because your creatinine is raised for a reason that has nothing to do with your kidneys. Creatine supplements, a lot of muscle, a heavy protein meal, hard training or dehydration all push creatinine up, and eGFR is calculated from creatinine. A Cystatin C test at R694 measures filtration without that interference.
Does creatine lower your eGFR?
On paper, yes. Creatinine is what creatine breaks down into, so supplementing raises serum creatinine by roughly 10 to 30% and the calculated eGFR falls accordingly. Controlled trials in healthy adults have not found that creatine harms the kidneys themselves. Either stop for 3 to 4 weeks before testing, or ask for Cystatin C instead.
Is eGFR measured or calculated?
Calculated. It's derived from your serum creatinine plus your age and sex, using a standard equation. Nothing about your kidneys is measured directly, which is why the result is only as reliable as the creatinine it's built on.
What is the functional range for eGFR, and how is it different?
A standard laboratory reference range is statistical: it is built so that about 95% of a reference population falls inside it, and it is designed to identify people who need treating. A functional or optimal range is narrower and asks whether a result is drifting in a direction that may matter over time, even while it stays inside the standard range. Functional optimal ranges are educational reference recommendations rather than diagnostic thresholds and are not universally agreed. A result inside a standard laboratory range is not a disease. Epicentre includes a functional health report with every blood order, showing each marker against both ranges alongside the standard laboratory result your doctor works from.
Other markers explained
This page is general health information and not a medical diagnosis. Epicentre Aids Risk Management (Pty) Ltd, practice number 1117394, provides diagnostic laboratory testing: we don't diagnose, prescribe or treat, and results are intended to inform a consultation with your doctor. Medically reviewed by Dr Samantha Naidoo, MB ChB, FCP (SA), Medical Director. Prices are 2026 cash rates including 15% VAT and can change without notice. Reference ranges vary between laboratories and your result prints with the range that applies to you.