Creatinine & eGFR
The standard kidney function markers on every blood test. But creatinine alone can mislead — especially if you're muscular or take creatine. Here's how to read yours properly.
Creatinine is a waste product from muscle metabolism that your kidneys filter out. When your kidneys aren't working well, creatinine builds up. eGFR uses your creatinine to estimate how efficiently your kidneys are filtering — correcting for age and sex. Together, they're the standard kidney health check.
What are creatinine and eGFR?
Your muscles constantly break down a compound called creatine phosphate for energy. The waste product — creatinine — enters your bloodstream and gets filtered out by your kidneys. If your kidneys are healthy, creatinine stays low. If they're struggling, it rises.
eGFR (estimated Glomerular Filtration Rate) takes your creatinine and plugs it into a formula that accounts for your age and sex. The result tells you approximately how many millilitres of blood your kidneys filter per minute. A higher eGFR = better kidney function.
The key limitation: creatinine is influenced by your muscle mass. A 90 kg man who lifts weights will naturally have higher creatinine than a 55 kg sedentary woman — even though both may have perfectly healthy kidneys. This is where eGFR helps, but even eGFR has limits in very muscular individuals.
What your number means
| eGFR (mL/min) | CKD Stage | What it means |
|---|---|---|
| >90 | Normal | Healthy kidney function |
| 60–89 | Stage 2 | Mildly decreased — monitor annually |
| 45–59 | Stage 3a | Mild-moderate decrease — needs attention |
| 30–44 | Stage 3b | Moderate-severe — nephrologist referral |
| <30 | Stage 4–5 | Severe — specialist management required |
If you take creatine monohydrate (a popular supplement), your creatinine will be artificially elevated by 0.1–0.3 mg/dL. This does NOT mean kidney damage. Tell your doctor about creatine use. For a more accurate kidney assessment, ask for cystatin C — a marker unaffected by muscle mass or creatine intake.
How to protect your kidneys
- Stay hydrated — 2–3 litres of water daily. Dehydration concentrates creatinine and stresses your kidneys.
- Control blood sugar — diabetes is the #1 cause of kidney disease in India. Keep HbA1c below 6.5% (ideally below 5.7%).
- Control blood pressure — hypertension is the #2 cause. Target below 130/80.
- Avoid chronic NSAIDs — ibuprofen, diclofenac, and other NSAIDs are widely used in India and are a common cause of preventable kidney damage. Use sparingly.
- Don't overdo protein if eGFR is low — if your eGFR is below 60, discuss protein intake with your doctor. For healthy kidneys, normal protein intake (1.2–1.6 g/kg) is safe.
- Annual testing — especially if you have diabetes, hypertension, or family history of kidney disease.
Watch your eGFR trend — not just single snapshots
eterni tracks your creatinine and eGFR over time — so you can catch declining kidney function early, when it's still reversible.
Get early accessFrequently Asked Questions
What is eGFR and why is it better than creatinine alone?
eGFR (estimated Glomerular Filtration Rate) is calculated from your creatinine level, adjusted for age, sex, and race. It estimates how much blood your kidneys filter per minute. eGFR is better than raw creatinine because creatinine is affected by muscle mass — a muscular person can have high creatinine with perfectly healthy kidneys. eGFR corrects for this.
Can creatine supplements raise creatinine?
Yes. Creatine monohydrate supplementation increases your body's creatine pool, and creatinine is a breakdown product of creatine. This can raise serum creatinine by 0.1–0.3 mg/dL without any actual kidney damage. If you take creatine, mention it to your doctor and consider cystatin C for a more accurate kidney function assessment.
What is a normal eGFR?
Normal eGFR is above 90 mL/min/1.73m². Between 60–89 is mildly decreased (Stage 2 CKD if other markers are abnormal). Below 60 for more than 3 months is classified as chronic kidney disease (Stage 3+) and needs monitoring. Optimal is above 90, and ideally above 100 in younger adults.
How can I protect my kidneys?
Stay hydrated (2–3 litres/day), control blood sugar and blood pressure (the two biggest kidney killers), avoid chronic NSAID use (ibuprofen, diclofenac), limit excessive protein only if eGFR is already low, and get annual kidney function checks especially if you have diabetes, hypertension, or a family history of kidney disease.
Why eGFR equations matter
The most commonly used equation in India is the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) formula, which replaced the older MDRD equation. CKD-EPI is more accurate at higher GFR levels (above 60) and uses creatinine, age, and sex. Some labs still report MDRD — if so, the values may differ slightly.
For people where creatinine-based eGFR may be inaccurate — very muscular individuals, people on creatine supplements, amputees, or those with unusual diets — cystatin C-based eGFR is the gold standard. Cystatin C is produced at a constant rate by all nucleated cells and isn't affected by muscle mass or diet.
Kidney disease in India — the silent epidemic
India has an estimated 17% prevalence of chronic kidney disease, but most cases are undiagnosed until late stages. The biggest risk factors are diabetes (which damages the kidney's filtering units) and hypertension (which damages the blood vessels supplying the kidneys). Early-stage CKD is reversible with proper blood sugar and blood pressure control. Late-stage CKD requires dialysis or transplant. Annual eGFR screening — especially if you have risk factors — is one of the highest-value preventive tests you can get.
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