Creatinine is the most common test used to check how well your kidneys are working. It is a waste product made by your muscles at a fairly steady rate, and your kidneys filter it out of the blood into the urine. When the kidneys filter well, blood creatinine stays low; when filtering slows, creatinine builds up. So a HIGH creatinine usually points to reduced kidney function.
It is reported in mg/dL in the United States. One thing to understand up front: creatinine depends partly on muscle mass, so a muscular young man and a frail older woman can both be perfectly healthy with very different creatinine values. This is exactly why labs also calculate eGFR from your creatinine — to adjust for these differences.
Typical creatinine reference ranges (mg/dL)
| Adult men | 0.7 – 1.3 | Higher end partly reflects more muscle |
|---|---|---|
| Adult women | 0.6 – 1.1 | Typically lower than men |
| Children | 0.3 – 0.7 | Rises gradually with growth |
Ranges differ by lab and method. A result just outside the range is interpreted alongside your eGFR, not in isolation.
What a high creatinine means
A creatinine above the reference range suggests your kidneys are filtering less effectively than expected. But before assuming kidney disease, it is essential to know that creatinine rises temporarily for many harmless or reversible reasons: dehydration, a recent heavy protein meal, intense exercise, certain supplements (creatine), and some medications. A single mildly raised value in someone who is dehydrated is very different from a persistently rising one.
When creatinine is genuinely and persistently elevated, it indicates reduced kidney function — which can be acute (a sudden, often reversible drop, for example from dehydration, infection, or medication) or chronic (a gradual long-term decline, commonly from diabetes or high blood pressure). The pattern over time matters far more than one reading: your doctor will look at whether it is stable, rising, or returning to normal.
From laboratory experience, the most useful habit is to never read creatinine alone. Always look at the eGFR calculated beside it, check whether urea/BUN moves in parallel, and compare to your previous results. A creatinine of 1.4 means something very different in someone whose baseline is 1.3 versus someone whose baseline is 0.8.
What a low creatinine means
A low creatinine is rarely a kidney concern and is usually not worrying. It most often reflects low muscle mass — common in older adults, during pregnancy, or in people who are underweight. Occasionally it accompanies liver disease or a very low-protein diet. In most cases a low creatinine needs no action, though your doctor will interpret it in the context of the rest of your report.
Why your creatinine changed since last time
Creatinine is sensitive to hydration and recent activity, so small fluctuations between tests are normal. A jump after a gym session, a day of poor fluid intake, or a high-protein meal can nudge it up without any change in kidney health. This is why doctors rarely act on a single borderline value — they repeat it under better conditions, or look at the trend across several results. A steady creatinine over months is reassuring even if it sits slightly above the printed range.
When to actually worry — and when not to
- A creatinine that is clearly above your usual baseline, or rising across repeated tests — show your doctor; the trend matters more than one value.
- High creatinine with a low eGFR (below 60) on the same report — this combination warrants medical review of kidney function.
- A sudden large rise in creatinine, especially with reduced urination, swelling, or after a new medication — contact your doctor promptly; this can signal acute kidney injury.
- A mildly high creatinine when you were dehydrated or had just exercised — often not significant; a repeat test under normal conditions usually clarifies it.
Common questions
Do I need to fast for a creatinine test?
Usually not, though it's often drawn as part of a panel that does require fasting. Avoiding a large meat meal and heavy exercise the day before gives a more representative result, since both can temporarily raise creatinine.
Does creatine supplement affect the creatinine test?
Yes — creatine supplements can modestly raise measured creatinine without any kidney problem, because creatine breaks down into creatinine. Mention it to your doctor so a raised value isn't misread.
Is creatinine the same as creatine?
No, though the names are confusingly similar. Creatine is a compound your muscles use for energy; creatinine is the waste product left over from it. The blood test measures creatinine.
One value never tells the whole story.
Upload your full lab report and get every value explained in plain language — in English, Arabic, Turkish, Italian, Spanish, Polish, French, or German. Classified as Normal, Borderline, Abnormal, or Critical. In seconds.
Upload your reportMedical disclaimer: This article is for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment. Reference ranges vary between laboratories — always compare your result to the range on your own report, and consult a qualified healthcare professional about your results and any symptoms.