Creatine and creatinine: why your blood test may look off

Yes, creatine can raise the creatinine level on a blood test and make your eGFR look lower, even when your kidneys are healthy. This happens because your body turns some creatine into creatinine every day, and eGFR is calculated from creatinine. Tell your doctor you take creatine before any blood test so they can read the result correctly.

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What is the difference between creatine and creatinine?

The names are almost the same, but the molecules do different jobs. Creatine is stored mostly in your muscles, where it helps recycle energy during short, hard efforts. Creatinine is what creatine becomes when it breaks down. It has no energy role. Your kidneys filter it out of the blood and you pass it in urine.

Creatine is not a lab test result on a normal blood panel. When a report shows "creatinine", it is measuring the waste product. Creatine kinase (often shown as CK) is also a different test. It is an enzyme released by muscle, and it can rise after hard training.

Does creatine turn into creatinine?

Yes, slowly and all the time. According to the International Society of Sports Nutrition, about 1–2% of the creatine in your muscles breaks down into creatinine each day. That is true whether or not you take a supplement. Taking creatine raises the amount stored in your muscles, so the amount broken down each day can rise too.

Creatine also changes into creatinine in liquid, and faster when the liquid is warm or acidic. In lab tests at room temperature, about 4% changed after 3 days at a mildly acidic pH, and more at higher acidity. Over the few minutes it takes to mix and drink a glass of water, the loss is very small. The dry powder is stable. See does creatine expire for storage details.

Why does creatine raise creatinine and lower eGFR?

Doctors rarely measure kidney filtration directly. Instead, a lab measures creatinine in your blood and uses a formula, with your age and sex, to estimate your glomerular filtration rate (eGFR). The formula assumes that creatinine is produced at a normal, steady rate. When you take creatine, more creatinine enters the blood. The formula reads that as the kidneys clearing less, so eGFR goes down on paper.

Research shows this pattern clearly. A 2025 meta-analysis found that creatine produced a small rise in serum creatinine but no significant change in GFR. In a 2010 case, a young man with one kidney took creatine for 35 days. His serum creatinine rose from 1.03 to 1.27 mg/dL and his estimated clearance fell, but his kidney function measured with an accurate lab method stayed the same. The authors noted that creatinine alone would have falsely suggested a problem.

A 2014 case report describes a man taking a creatine ethyl ester product whose creatinine was high enough to look like serious kidney failure. His values moved back toward normal about two weeks after he stopped. Muscle mass, hard exercise, and a large meat meal can also raise creatinine, so a single result is never the full story.

Should you stop creatine before a blood test?

There is no official rule, and there is no agreed number of days to stop. The most important step is simple: tell the person ordering the test that you take creatine, how much, and for how long. A clinician who knows this can interpret a mildly raised creatinine with that in mind.

If your doctor wants a reading without the creatine effect, they may ask you to pause for a while and repeat the test. Follow their advice on timing. Stopping creatine is harmless, and your muscle stores fall back slowly over several weeks (see what happens when you stop creatine). If your test requires fasting, follow the clinic's fasting instructions. If you are not sure whether a creatine drink counts, skip it that morning and take it after the test.

Do not stop or change any prescribed medicine because of a creatinine result without talking to your doctor.

What is cystatin C and why can it help?

Cystatin C is a small protein that the body makes at a fairly steady rate. Like creatinine, it is filtered by the kidneys, so it can also be used to estimate kidney function. Unlike creatinine, it is not a breakdown product of creatine and depends much less on muscle mass.

A large 2012 study in the New England Journal of Medicine found that an equation using both creatinine and cystatin C estimated kidney function more accurately than either marker alone. If your creatinine is raised and you take creatine, ask your doctor whether a cystatin C test, or an eGFR based on both markers, makes sense for you.

When is a high creatinine worth checking?

Creatine explains a small rise in creatinine, not every abnormal result. A large change, a result that keeps rising, protein or blood in your urine, high blood pressure, swelling, or less urine than usual all need proper medical follow-up. People with known kidney disease should not assume that creatine is the cause. Our guide to creatine and kidney health covers what is known in more detail.