What does an eGFR of 90 mean?
An eGFR of 90 mL/min/1.73m² sits in the top band of the KDIGO scale, stage G1, which is labelled "normal or high" filtering. A result here does not, on its own, point to reduced kidney function. It is still only half of a kidney check — a urine test for albumin is the other half — and one blood test on one day is always just a snapshot of that day.
90 mL/min/1.73m² is the conventional unit used by KDIGO and by most labs worldwide. In SI units the same result is about 1.50 mL/s/1.73m², because 1 mL/min/1.73m² equals roughly 0.0167 mL/s/1.73m². Many labs do not print an exact figure at the top of the range and simply report ">90" or ">60" instead.
What this test measures
eGFR stands for estimated glomerular filtration rate. Each kidney holds around a million microscopic filters, and eGFR is an estimate of how much blood those filters clean every minute. The "1.73m²" part means the figure has been adjusted to a standard adult body size, so results can be compared between people. Nothing is measured directly. The lab measures creatinine, a waste product your muscles release into the blood all day long, and a formula turns that into an estimate using your age and sex. Because it is an estimate, several things unrelated to your kidneys can nudge it: how much muscle you carry, a very high or very low meat intake, pregnancy, dehydration, a recent illness, and some medicines. Different labs also use slightly different versions of the formula, so the same blood sample can give slightly different numbers in different places.
Where 90 mL/min/1.73m² sits
The KDIGO chronic kidney disease guideline sorts eGFR into "G stages", all measured in mL/min/1.73m²: G1 is 90 or above (normal or high), G2 is 60–89 (mildly decreased), G3a is 45–59, G3b is 30–44, G4 is 15–29, and G5 is under 15. A result of 90 sits at the entry point of G1, the top band. One thing that surprises many people: KDIGO does not allow a single blood test to stage chronic kidney disease. Staging needs the eGFR to stay in the same band for more than three months, and it needs a second piece of information — a urine test measuring albumin (a protein that leaks through damaged filters). eGFR is only one axis of the KDIGO chart; albumin is the other. Only a doctor who can see both, plus your history and past results, can say what your number means for you.
What to do next
- Take the result back to the doctor or clinic that ordered it. They can read it beside your past results, your urine test and your medical history, which is the only way to interpret it properly.
- Ask whether a urine albumin test (often written as ACR, albumin-to-creatinine ratio) has been done. Without it, an eGFR number is only half of a kidney check.
- Dig out any older kidney results you have. The direction the number has moved over years tells a doctor far more than any single reading.
- Ask when, or whether, the test should be repeated. Repeat testing is routine and is not a sign that something is wrong.
- If anything about the report worries you, write your questions down before your appointment rather than searching for more numbers online.
Common questions
Is an eGFR of 90 good?
It sits in the top KDIGO band, G1, which is labelled normal or high filtering. Most doctors would not act on a 90 on its own. It is not a certificate of perfect kidney health, though, because early kidney damage can show up as protein in the urine while eGFR still looks normal.
Does an eGFR of 90 mean I definitely do not have kidney disease?
Not by itself. KDIGO defines chronic kidney disease using two things — filtering rate and signs of kidney damage — so it is possible to have a normal eGFR alongside albumin in the urine or a structural problem seen on a scan. Your doctor is the only person who can check both halves and answer this for you.
My eGFR dropped from 110 to 90. Should I worry?
A change of this size between tests is common and often means nothing. Creatinine shifts with hydration, diet, muscle and even the time of day, and different labs use different formula versions. Mention it to your doctor so they can look at the overall trend rather than at one point on a graph.
Why does my report just say ">90" instead of a number?
The formulas behind eGFR are least accurate at the top of the range, so many labs stop reporting an exact figure above a cut-off. It is a lab reporting habit, not information being kept from you.
Does eGFR go down as you get older?
On average, yes — it tends to drift down slowly from around age 30 to 40 in most people. That is why a figure that would prompt questions in a 25-year-old can be unremarkable at 70. Your doctor reads the number against your age, not against a single universal target.
Can drinking more water raise my eGFR?
Being badly dehydrated can make one reading look worse than usual, so being normally hydrated helps the test be fair. But drinking large amounts of water is not a way to improve how well kidneys filter, and drinking far more than thirst calls for can cause problems of its own. Ask your doctor what is sensible for you.