Creatinine and eGFR: What Your Kidney Report Really Says
Posted 18 Sep 2026 | Source:
Nearly every kidney conversation I have starts with two numbers on a report: creatinine, and eGFR. They sit next to each other, they move in opposite directions, and they get misread constantly — in both directions. I see people badly frightened by a result that is unremarkable for them, and I see people reassured by one that deserved a much closer look. Here is what each number means, and what I would want you to ask me about yours.
Creatinine is a waste product, not a diagnosis
Your muscles produce creatinine continuously as they use energy. It goes into the blood and your kidneys clear it into the urine. If clearance drops, it builds up and the level rises. That makes it useful. It also makes it imperfect, because the level depends on how much creatinine you make, not only on how well you clear it.
A muscular young man and a frail elderly woman can have identical true kidney function and quite different creatinine values. It runs the other way too: someone with very little muscle can show a creatinine that looks comfortable while their kidney function is genuinely reduced. I have to hold that in mind every time I read one.
This is why the laboratory reports creatinine in mg/dL (µmol/L) and then calculates something else from it.
eGFR is an estimate, and I mean estimate
The estimated glomerular filtration rate takes your creatinine and adjusts it for your age and sex, to approximate how much blood your kidneys are filtering each minute. It is a better guide than creatinine alone.
It is still an approximation, and it performs less well in some situations — at the extremes of body build, in pregnancy, when your muscle mass is unusual, during acute illness, and when your kidney function is moving rather than sitting stable.
When I need to check the estimate, I can measure a different blood marker called cystatin C, which is not affected by muscle mass in the same way. Whether that is worth doing for you is a decision I would make case by case.
I will not diagnose you from one result
Chronic kidney disease is defined by an abnormality that has lasted at least three months. One reduced eGFR is a reason for me to look again. It is not a diagnosis.
A fair number of things push creatinine up temporarily with no lasting damage at all:
- Dehydration, from heat, poor intake or a stomach upset
- Any acute illness
- Anti-inflammatory painkillers, especially taken regularly or just before the test
- A recent contrast scan
- Certain medicines that block creatinine's exit route without changing the actual filtration — the number rises while the kidney is working exactly as before
- A heavy protein meal, or creatine supplements, shortly before the sample
So if your report has changed and nobody has repeated it, ask when it should be repeated and under what conditions.
The number missing from most reports I am shown
An eGFR tells me your capacity. It tells me nothing about whether the filter is leaking. For that I need a urine albumin-to-creatinine ratio.
The KDIGO 2024 international guideline stages kidney disease using both together, because your risk depends on the combination. Two people with the same eGFR can face very different futures depending on their albuminuria.
I will be blunt about this: patients often arrive at a first kidney consultation with years of creatinine values and not one urine albumin result. If that describes your file, ask why.
Why I care more about the trend than today's number
A single eGFR tells me where you are. A run of them tells me where you are heading, and the direction usually matters more than the position.
An eGFR that has not moved in four years is a completely different situation from the same number reached after a steady fall. So bring me your old reports — all of them, from every hospital. I can only see a trend if I can see the points.
One caution while you compare them yourself: results from different laboratories are not always perfectly interchangeable, and different equations give slightly different estimates. A small gap between two labs is not necessarily a change in you.
What these numbers actually change
Your eGFR and your albuminuria together influence:
- How often I want to see you
- Which medicines are suitable, and at what dose
- Whether scans and procedures need precautions
- Whether you need a kidney specialist at all
- When I start conversations about longer-term treatment options — and I would rather start those early and unhurried than late and under pressure
What they do not tell me is how you feel or how long you will live. Numbers shape the plan. They are not the plan.
Three questions for your next visit
- What is my eGFR trend over the last few years, not just today?
- What is my urine albumin, and what do the two mean together?
- How often should I be checked, and what would make that change sooner?
Bring every old report you have, and your full medicine list — painkillers, ayurvedic and herbal preparations, supplements included.
Frequently asked questions
Q: Does a high creatinine always mean kidney disease?
A: No. Muscle mass, dehydration, some medicines and recent illness can all raise it. What defines chronic kidney disease is an abnormality that persists for at least three months.
Q: Which matters more, creatinine or eGFR?
A: For describing kidney function, eGFR is generally the more useful of the two, because it adjusts for age and sex. Both should be read alongside a urine albumin result.
Q: My eGFR dropped by 3 points. Should I worry?
A: Small fluctuations between tests are common and can reflect hydration, timing or laboratory variation. A sustained trend matters far more than one step. Ask for it to be read against your previous results.
Q: Can eGFR go back up?
A: It can, if the cause was temporary — dehydration or a medicine effect, for instance. Whether improvement is likely in your case depends on the cause.
Q: Do I need a 24-hour urine collection?
A: For most routine purposes, no. Blood estimates with a urine albumin ratio have replaced it, though there are specific situations where a timed collection still helps.
