Kidney Health Tests: Creatinine, eGFR & Urine

Quick answer

Healthy kidneys filter waste, balance salts and keep protein out of urine; the earliest warning sign of damage is tiny amounts of albumin leaking into urine (microalbuminuria), especially in diabetes and hypertension. The core takeaway: eGFR and urine albumin together define kidney health and its stages, and catching changes early is when treatment helps most.

Kidney health tests at a glance

Chronic kidney disease usually has no symptoms until damage is advanced, so these tests do the catching. Blood tests measure what the kidney fails to remove; urine tests measure what it fails to retain.

Test	Normal	What it checks
Serum creatinine	Men 0.74–1.35 mg/dL; women 0.59–1.04 mg/dL	Kidney filtering efficiency
eGFR	>90 mL/min/1.73m²	Estimated filtering rate, corrected for age and sex
BUN	7–20 mg/dL	Protein waste in blood
BUN:creatinine ratio	10:1 – 20:1	Helps separate dehydration from true kidney damage
Urine microalbumin (ACR)	<30 mg/g creatinine	Earliest sign of kidney damage — leaks years before creatinine rises
Serum electrolytes	Na 136–145, K 3.5–5.0 mEq/L	Fluid and salt balance
Uric acid	Men 3.5–7.2; women 2.6–6.0 mg/dL	Gout and kidney stone risk

The complete kidney test panel

Test	Normal	What it checks
Serum Creatinine	Men: 0.74–1.35 mg/dL; Women: 0.59–1.04 mg/dL	Kidney filtering efficiency
eGFR	>90 mL/min	% of kidney function remaining
Blood Urea Nitrogen (BUN)	7–20 mg/dL	Protein waste in blood
BUN:Creatinine Ratio	10:1 – 20:1	Dehydration vs kidney damage
Urine Routine	No protein, no RBC	Kidney leakage
Urine Microalbumin	<30 mg/g creatinine	Earliest sign of kidney damage
Serum Electrolytes	Na 136–145, K 3.5–5.0 mEq/L	Fluid and salt balance
Uric Acid	Men: 3.5–7.2 mg/dL; Women: 2.6–6.0 mg/dL	Gout and kidney stones risk

Key points

Microalbuminuria (30 to 300 mg/g) is the earliest sign of diabetic or hypertensive kidney damage.
eGFR plus urine albumin together define kidney health and CKD stages.
High-risk groups (diabetes, hypertension) need regular checks.
Early changes are when treatment helps most.

Who should get regular kidney tests?

Diabetics: diabetes is the leading cause of kidney failure worldwide. Annual creatinine + urine microalbumin from diagnosis
Hypertensives: high blood pressure is the second leading cause. Annual KFT
People taking NSAIDs regularly: ibuprofen, diclofenac, naproxen all damage kidneys with prolonged use
People taking contrast dye for CT scans: contrast nephropathy risk
Anyone with recurrent kidney stones: 24-hour urine study + metabolic workup
Family history of kidney disease: polycystic kidney disease is hereditary

The most important early warning sign: urine microalbumin

Microalbuminuria: catch kidney damage years early

Normal kidneys do not let albumin (a large protein) escape into urine. The earliest sign of diabetic or hypertensive kidney damage is tiny amounts of albumin leaking through (microalbuminuria: 30–300 mg/g creatinine). This is detectable years before creatinine rises or eGFR drops. At the microalbuminuria stage, kidney damage is almost completely reversible with tight blood pressure and sugar control. Once creatinine rises significantly, damage is mostly irreversible, which is why early testing matters so much.

Questions to ask your doctor

What is my eGFR, and what does that mean for my kidney function percentage?
Should I test urine microalbumin given my diabetes/hypertension?
Which pain medications are safe for me to take?
Do I need a kidney ultrasound?

eGFR, what the number means and how it's calculated

Estimated glomerular filtration rate (eGFR) is the standard measure of overall kidney function.²³ It estimates how much blood the kidneys filter per minute, per 1.73 m² of body surface area. The two main equations used in the UK:

CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration): Uses serum creatinine, age, and sex. More accurate at eGFR above 60 than the older MDRD equation. Replaced MDRD as the UK standard in 2021.
CKD-EPI with cystatin C: More accurate in patients where creatinine is unreliable, particularly very muscular athletes (overestimates kidney function with creatinine alone) or cachexic/elderly patients (underestimates impairment). NICE recommends cystatin C-based eGFR when creatinine-based results seem inconsistent with clinical status.

CKD staging by eGFR (alongside urine ACR): G1 ≥ 90, G2 60–89, G3a 45–59, G3b 30–44, G4 15–29, G5 below 15 (kidney failure, usually requiring renal replacement therapy). A diagnosis of CKD requires the eGFR abnormality to persist for more than 3 months.

Urine tests, albumin and protein leakage

Blood tests measure what the kidney fails to remove; urine tests measure what it fails to retain:

Urine albumin-to-creatinine ratio (ACR): The primary urine test for detecting early kidney damage. Even small amounts of albumin in urine (microalbuminuria, ACR 3–30 mg/mmol) indicate glomerular damage, seen earliest in diabetic nephropathy, hypertensive kidney disease, and lupus nephritis. ACR above 30 mg/mmol = macroalbuminuria (significant proteinuria). First morning urine gives the most reproducible result. ACR classifies albuminuria: A1 (below 3), A2 (3–30), A3 (above 30).
Urine protein-to-creatinine ratio (PCR): Measures all urinary proteins (not just albumin). PCR above 100–150 mg/mmol indicates clinically significant proteinuria warranting nephrology review. Nephrotic syndrome (PCR above 350 mg/mmol, hypoalbuminaemia, oedema) is a medical emergency requiring urgent renal biopsy to determine cause (minimal change disease, focal segmental glomerulosclerosis, membranous nephropathy).
Urine microscopy: Red cell casts in urine (red blood cells trapped in protein cylinders) are virtually pathognomonic of glomerulonephritis, an inflammatory kidney condition requiring urgent immunosuppression. White cell casts indicate pyelonephritis (kidney infection) rather than bladder infection.

Kidney testing myths vs facts

MYTH Normal creatinine means your kidneys are healthy.

Fact: Creatinine rises only after substantial function is lost, and it is skewed by muscle mass. eGFR corrects for that — and the urine albumin test can detect damage years before either blood marker moves.

MYTH Kidney disease always has noticeable symptoms early.

Fact: Chronic kidney disease is famously silent until it is advanced. That is exactly why diabetics and hypertensives are advised to get annual kidney checks from diagnosis, not when symptoms appear.

MYTH One low eGFR means you have chronic kidney disease.

Fact: CKD requires the abnormality to persist for more than three months. A single low reading can follow dehydration, a recent illness or certain medicines — it must be repeated before it means anything.

MYTH Urine colour tells you everything about kidney health.

Fact: Albumin leaking into urine at the earliest damage stage is invisible to the eye. Microalbuminuria (30–300 mg/g) needs a laboratory ACR test; no amount of colour-checking replaces it.

What matters most in kidney testing

Read eGFR and urine albumin together. eGFR shows current function; albumin shows early damage. Either alone is half the picture.
Confirm over three months. One abnormal reading is a prompt to repeat, not a diagnosis of chronic kidney disease.
Know your risk group. Diabetes, hypertension, regular NSAID use, family history of kidney disease — these are the reasons to test regularly.
Watch potassium. As kidneys decline they retain potassium, and levels above 6.0 mEq/L are a genuine emergency.

Practical notes

Check with your doctor about holding strenuous exercise and creatine supplements for a day or two before testing, since both can raise creatinine. Arrive normally hydrated and note the time of your last meal, since some kidney panels are drawn fasting.

Bring your full medicine list — especially blood pressure drugs, diuretics, and painkillers — past kidney reports for trend comparison, and a note of any symptoms such as swelling or changes in urination. The doctor interprets the numbers against your symptoms, not in isolation.

Kidney assessment combines blood tests (creatinine/eGFR), urine tests (albumin/protein), and sometimes imaging — no single test stands alone. Ask your doctor which of the three your results cover and whether anything is missing from the picture.

For follow-up, ask about blood pressure and diabetes control in the context of kidney protection, when to retest, and whether a nephrology referral is warranted at your stage.

In India

Kidney health check panels that include urine tests are typically ₹1,000–₹3,000, though prices vary by city and lab. Confirm that the panel includes a urine albumin or protein test — some budget panels skip it.

Choose NABL-accredited labs; home sample collection is available in major cities. The reference range printed on your own report is the one that counts, since methods and ranges differ between labs.

Frequently Asked Questions

Which tests show how well my kidneys work?

Creatinine and the calculated eGFR are the core measures of kidney function, while an urine albumin:creatinine ratio (ACR) detects early kidney damage before function declines.

What is eGFR and what's a normal value?

eGFR estimates how well the kidneys filter blood. Above 90 is generally normal, while values below 60 for more than three months indicate chronic kidney disease.

Can kidney damage be present with normal blood tests?

Yes. Early kidney damage often shows first as protein (albumin) leaking into the urine, which is why the urine ACR test is important alongside blood tests, especially in diabetes and high blood pressure.

Is a urine test really necessary if my blood kidney tests are normal?

Yes — it adds information blood tests miss. Albumin in urine can appear before blood markers change, especially in diabetes and hypertension. It is a simple test that completes the picture, so ask your doctor to include it if it was not ordered.

I was told to collect a 24-hour urine sample — any tips?

Follow the lab's instructions exactly: start by discarding the first morning urine and noting the time, then collect everything for the next 24 hours, keeping the container cool as instructed. An incomplete collection makes the result unreliable, so plan it for a day you will be home.

Can kidney damage be reversed if caught early?

Some causes are treatable and early stages can be stabilized, but this depends entirely on the cause and the stage — only your doctor can say for your situation. What is well established is that early detection, plus blood pressure and diabetes control, gives the kidneys the best chance, which is the point of regular testing.

My eGFR dropped a little since last year — should I worry?

Small shifts can come from hydration, muscle changes, lab variation, or a real trend — your doctor reads it against your history, medicines, and urine results. Bring both reports and ask whether the change is meaningful for you and what the plan is.

References

Sources cited on this page. PubMed links open the original abstract.

Levey AS, Coresh J. Chronic kidney disease. Lancet. 2012;379(9811):165–180. PMID 21840587 · doi:10.1016/S0140-6736(11)60178-5
Levey AS, Coresh J, Balk E, et al. "National Kidney Foundation practice guidelines for chronic kidney disease: evaluation, classification, and stratification." Ann Intern Med. 2003;139(2):137–147. PMID 12859163 · doi:10.7326/0003-4819-139-2-200307150-00013
Levey AS, Eckardt KU, Dorman NM, et al. "Nomenclature for kidney function and disease: report of a Kidney Disease: Improving Global Outcomes (KDIGO) Consensus Conference." Kidney Int. 2020;97(6):1117–1129. PMID 32409237 · doi:10.1016/j.kint.2020.02.010

Medical Disclaimer: This page is for general educational purposes only. It does not constitute medical advice. Always consult a qualified doctor before making any health decisions.