Kidney health is assessed with two simple, inexpensive tests: a blood test that estimates how well your kidneys filter, and a urine test that checks whether they are leaking protein. Together they tell your doctor the stage and cause of any kidney problem.
eGFR — your kidney "filtering score"
The estimated Glomerular Filtration Rate (eGFR) estimates how many millilitres of blood your kidneys clean each minute. It is calculated from your blood creatinine, age and sex. A higher number is better.
| eGFR | What it suggests |
|---|---|
| 90+ | Normal kidney filtering |
| 60–89 | Mildly reduced (normal if no other signs) |
| 30–59 | Moderately reduced function |
| 15–29 | Severely reduced function |
| Below 15 | Kidney failure |
Serum creatinine
Creatinine is a waste product from muscle activity that healthy kidneys remove. When kidney function falls, creatinine rises in the blood. Because it depends on muscle mass, creatinine is always interpreted alongside eGFR rather than on its own.
Blood urea (BUN)
Urea is another waste product filtered by the kidneys. It can rise with reduced kidney function, but also with dehydration or a high-protein diet, so it is read in context.
Urine ACR — checking for protein leak
The Albumin-to-Creatinine Ratio (ACR) measures albumin (a protein) in a urine sample. Healthy kidneys keep protein in the blood; a leak is one of the earliest signs of kidney damage.
| Urine ACR (mg/g) | Meaning |
|---|---|
| Below 30 | Normal |
| 30–300 | Moderately increased (early damage) |
| Above 300 | Severely increased |
The two numbers that matter most
Modern kidney care stages disease using both eGFR and ACR together. Knowing both gives a far more accurate picture than either one alone.
A walkthrough of a typical kidney function report.
How often should I be tested?
If you have diabetes, high blood pressure, heart disease, or a family history of kidney failure, an annual eGFR and urine ACR is generally recommended. Your doctor may test more often if results are abnormal.
References & Further Reading
- National Kidney Foundation. "Tests to Measure Kidney Function, Damage and Detect Abnormalities." kidney.org
- KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD. kdigo.org
- NIDDK, National Institutes of Health. "Kidney Testing: Everything You Need to Know." niddk.nih.gov
This article is for general education only and does not replace personalised medical advice. Always review your results with a qualified physician.