Also seen on reports as: Serum Cr, Plasma Creatinine, S. Creatinine
What is Creatinine?
Creatinine is a waste product made by muscles as part of normal energy use. It is released into the blood at a fairly steady rate and is removed almost entirely by the kidneys. So the level of creatinine in the blood reflects how well the kidneys are clearing waste — when the kidneys are working well, creatinine stays low; when filtering slows down, it rises.
Because creatinine production depends on muscle mass, the same kidney function gives a different creatinine level in different people. A lean older woman makes less creatinine than a young man with more muscle, so the same blood level can mean different things in the two people. This is part of why doctors often look at creatinine alongside eGFR (an age-, sex-, and creatinine-based estimate of kidney filtering) rather than at creatinine alone.
The test is run on a small blood sample drawn from a vein. NABL-accredited Indian labs report serum creatinine in milligrams per decilitre (mg/dL).
Why doctors order it
Creatinine is part of almost every routine blood-test panel — annual health checks, pre-operative assessments, antenatal panels, and ICU monitoring. It is the most widely used single marker of kidney function and the basis for the eGFR calculation that appears on most lab reports.
Doctors order creatinine specifically when there are signs that might point to kidney involvement — swelling of legs or face, unusual tiredness, blood or foam in urine, reduced urine output, very high or very long-standing blood pressure, long-standing diabetes, or unexplained anaemia. It is also rechecked when starting or changing medications that pass through or affect the kidneys.
In Indian practice, creatinine is monitored particularly closely in people with diabetes (the leading cause of chronic kidney disease in India), with long-standing hypertension, and in those taking long-term medications known to affect the kidneys — including some anti-tuberculosis drugs, certain antibiotics, contrast dye for scans, and many traditional or ayurvedic preparations.
What the result means
A normal creatinine usually suggests the kidneys are filtering well — but normal in someone with low muscle mass (an older lean woman, a frail patient) can still hide reduced kidney function. This is one reason eGFR, age, sex, and body build are factored in.
A raised creatinine can mean kidney function has dropped (acutely or chronically), or that the body is producing more creatinine for non-kidney reasons — for example, a very high muscle-mass person, after intense exercise, or with some medications that block creatinine secretion without truly affecting filtering. Doctors look at the trend across multiple tests, urine findings, and ultrasound rather than relying on a single value.
A dropping creatinine over time is usually a good sign — but in someone losing significant muscle mass (illness, weight loss, immobility), creatinine can fall even as kidney function stays the same or declines. This is why creatinine in isolation can mislead, and why guidelines recommend pairing it with eGFR and urine tests.
Reference range
Values in mg/dL — adult non-pregnant ranges
- Adult men — typical range
- Roughly 0.7 – 1.3 mg/dL
- Adult women — typical range
- Roughly 0.6 – 1.1 mg/dL
- Mild rise
- Slightly above the upper limit — often non-specific, check trend and clinical context
- Moderate-to-significant rise
- Suggests reduced kidney function — usually paired with low eGFR
- Pregnancy
- Naturally lower than non-pregnant range — pregnancy ranges apply
Creatinine interpretation in Indians is complicated by lower-than-Western-average muscle mass, which can make eGFR formulas overestimate true kidney function. Doctors interpret creatinine in context — alongside eGFR, urine tests, age, build, and trend over time.
In India
What this test means for an Indian reader
Indians generally have lower muscle mass than the Western populations the eGFR formulas (CKD-EPI, MDRD) were calibrated on, which can cause those formulas to overestimate kidney function — sometimes meaningfully so. Doctors interpret creatinine alongside age, build, and clinical context, and may add a cystatin-C test in borderline cases.
There is no widely-adopted Indian-specific eGFR equation in routine clinical use. NABL-accredited labs report CKD-EPI eGFR as standard alongside the raw creatinine value.
Indian guidelines & references
- Indian Society of Nephrology (ISN)
- ICMR CKD screening guidelines
- AIIMS Nephrology clinical protocols
Common factors that affect the result
Muscle mass is the biggest source of variation. A heavily built person or someone on a high-protein diet typically has a slightly higher baseline creatinine; a lean older person typically has a lower baseline. Significant muscle loss from illness, immobility, or weight loss lowers creatinine without any improvement in kidney function. Bodybuilding supplements containing creatine raise creatinine directly.
Several common medications nudge creatinine. Some — including the antibiotic trimethoprim, cimetidine (an acid-lowering medication), and certain anti-cancer drugs — block creatinine secretion into urine without changing actual kidney filtering, raising the blood level without true kidney injury. Others — NSAIDs (ibuprofen, diclofenac, etc., very commonly used in India for pain), some antibiotics (aminoglycosides), contrast dye, and some ayurvedic / herbal preparations — can genuinely reduce kidney function.
Hydration matters. Significant dehydration raises creatinine because filtering drops temporarily; rehydration usually restores the level. Acute illness, fever, vomiting, or diarrhoea can transiently raise creatinine through this mechanism. The reading is more reliable when drawn on a normal hydration status, not after a heavy workout or a long fast in heat.
When to talk to your doctor
- Your creatinine is above the lab's upper limit, particularly if your eGFR has also dropped below 60 mL/min/1.73 m².
- Your creatinine has risen by more than ~25–30% from your usual baseline, even if it is still within the lab's reference range.
- You have diabetes, hypertension, recurrent UTIs, or a family history of kidney disease — these are situations where small creatinine changes matter earlier.
- You are on, or about to start, medications that affect the kidneys — anti-TB regimens, long-term NSAIDs, certain antibiotics, contrast dye for scans, or chemotherapy.
- You have swelling of legs or face, foamy urine, very high blood pressure, or unexplained tiredness alongside a raised creatinine.
Related tests
Sources
- Indian Society of Nephrology — CKD Clinical Practice Guidelines — Indian Society of Nephrology
- ICMR CKD Screening Guidelines — Indian Council of Medical Research
- KDIGO Clinical Practice Guidelines for CKD — Kidney Disease: Improving Global Outcomes
- AIIMS Nephrology Clinical Protocols — All India Institute of Medical Sciences
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