In short
Creatinine, urea and eGFR describe filtering; urine albumin describes leaking. A report can be normal on one and abnormal on the other, and knowing which is which tells you how urgent the result really is.
Emergency if: A markedly high potassium result, or palpitations and muscle weakness alongside poor kidney numbers — this affects heart rhythm and needs emergency care.
On your report
Creatinine, eGFR (Estimated Glomerular Filtration Rate), Urea / BUN, Urine Albumin-to-Creatinine Ratio (UACR) +3 more
On this page
01
Two different questions about one organ
Kidney testing rests on two measurements that are often confused. A blood test estimates how fast the kidneys filter, reported as eGFR and calculated from creatinine. A urine test measures whether protein is leaking through the filter, reported as the albumin-to-creatinine ratio. Filtering speed and leakiness are independent — early kidney damage in diabetes typically shows as leaking protein while filtering is still perfectly normal.
This is why a report with a reassuring creatinine can still be an early warning if the urine albumin is raised, and why guidance recommends both tests rather than either one. If your report only has blood numbers, the urine test is the reasonable thing to ask for.
02
Creatinine and what eGFR does with it
Creatinine is a waste product from normal muscle turnover that healthy kidneys clear steadily. Because production depends on muscle mass, the same creatinine value means different things in a heavily built young adult and in a frail older person — which is exactly the problem eGFR is designed to solve. The estimate adjusts the raw creatinine for age and sex to give a filtering rate that is comparable between people.
An eGFR of 60 or more is in the normal range. Below 60 may mean kidney disease, and 15 or less is described as kidney failure. One reading below 60 is not a diagnosis, though: chronic kidney disease requires the change to persist for at least three months, because dehydration, a recent illness and some medicines can push a single reading down temporarily.
03
Urea, and why it moves for non-kidney reasons
Urea — printed as blood urea or BUN — is the nitrogen waste from protein breakdown. It rises when the kidneys filter poorly, but also whenever the body is short of fluid, after a high-protein intake, during bleeding into the gut, and with steroid treatment. Because of that it is the least specific line on the panel.
Doctors often look at urea and creatinine together rather than separately. Urea rising out of proportion to creatinine usually points away from intrinsic kidney damage and towards dehydration or reduced blood flow to the kidneys — a distinction that changes the treatment completely, since one needs fluids and the other needs investigation.
04
Urine albumin: the early warning line
The urine albumin-to-creatinine ratio catches damage years before filtering slows. A ratio of 30 mg/g or less is normal; more than 30 mg/g may be a sign of kidney disease. The creatinine in the denominator corrects for how dilute the sample was, which is why a random sample works and a full day's collection is rarely needed now.
A single raised ratio is repeated before it means anything, because fever, heavy exercise in the previous day, a urine infection and menstrual blood all raise it temporarily. Two of three samples raised over three months is the usual bar for calling it persistent.
05
The rest of the panel, and what to do with the result
Most kidney panels also print sodium, potassium, bicarbonate, calcium, phosphorus and uric acid. These are less about diagnosing kidney disease and more about its consequences: as filtering falls, potassium and phosphorus tend to rise and bicarbonate to fall. Potassium is the one with immediate significance, because a markedly high value affects heart rhythm and is acted on the same day.
If your eGFR is below 60 or your urine albumin is raised, the practical follow-up is blood pressure control, a review of every medicine that is cleared by the kidneys or irritates them — anti-inflammatory painkillers being the common culprit — and a repeat in three months. Early kidney disease causes no symptoms at all, so the numbers are doing work your body is not.
When to act
Routine — see a doctor
A first eGFR between 45 and 59 with no symptoms: repeat in about three months with a urine albumin test before anything is called chronic.
Same-day — call promptly
Passing much less urine than usual, swelling of the face or legs appearing over days, or a creatinine that has jumped sharply from your last report.
Emergency — act now
A markedly high potassium result, or palpitations and muscle weakness alongside poor kidney numbers — this affects heart rhythm and needs emergency care.
Values mentioned in this story
Each one opens a visual guide with its normal range and what moves it — upload a report and we place your own numbers on the same scale.
Sources
- Chronic Kidney Disease Tests and Diagnosis — NIDDKniddk.nih.gov
- Creatinine Test — MedlinePlusmedlineplus.gov
- Glomerular Filtration Rate (GFR) Test — MedlinePlusmedlineplus.gov
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