If your blood test says “creatinine high,” creatine supplements may be part of the explanation—but that result alone cannot tell you whether your kidneys are injured. Creatine is converted into creatinine, a waste product measured in blood tests. Because clinicians also use creatinine to estimate kidney filtration, supplement use can complicate how the result is read.
Why Creatine Can Affect a Creatinine Blood Test
Your body naturally makes creatine, and you can also get it from food or supplements. Some creatine is broken down into creatinine. When a supplement increases the body’s creatine stores, creatinine in the blood may rise too, without a matching loss of kidney filtration.
Creatinine is useful because the kidneys filter it from the blood. A blood creatinine result is often used to calculate estimated glomerular filtration rate (eGFR), a measure of how well the kidneys filter. If creatinine rises for a reason other than reduced filtration, the creatinine-based eGFR may look lower than your actual kidney function. That is a limitation of the estimate—not proof that the kidneys are healthy or damaged.
What “Creatinine High” Can Mean When You Take Creatine
A 2025 systematic review and meta-analysis by Elham Kabiri Naeini and colleagues examined human studies published from 2000 through March 2025. The review included 21 studies; 12, with 177 participants taking creatine and 263 controls, contributed to the analysis of blood creatinine. The researchers found a small increase in creatinine overall, but no statistically significant change in glomerular filtration rate (GFR), which measures kidney filtering capacity.
That combination supports the possibility that creatine can raise the lab marker without reducing filtration. It does not show that every high result in a creatine user is harmless. The studies varied, and the pooled GFR result means the analysis did not detect a significant change; it does not prove that risk is zero for every person, dose, or health condition. Evidence is also more limited for people who already have kidney disease.
A 2023 review by Igor Longobardi, Bruno Gualano, Antonio Carlos Seguro, and Hamilton Roschel likewise explains that creatine can raise creatinine through normal metabolism and that controlled trials—many involving healthy people—have generally not found impaired kidney function. The authors note that further study is needed in people with pre-existing kidney disease. Taken together, these findings make a supplement-related rise plausible, but they do not replace an individual assessment.
How Clinicians Can Check Whether Kidney Function Is Affected
Clinicians interpret a creatinine result in context rather than treating one number as a diagnosis. They may compare it with your previous results, consider when you started creatine, and look at other indicators of kidney health. Depending on your situation, these can include urine tests for albumin or protein and a blood test for cystatin C, another marker used to estimate GFR. A clinician may also consider a directly measured GFR in settings where a more precise assessment is needed; that test is less routinely available.
Cystatin C can be useful when a creatinine-based estimate may be misleading, but it is not a substitute for clinical judgment. The right follow-up depends on your results and health history. A rising creatinine, a change in other kidney markers, or a result that stays abnormal should not automatically be attributed to a supplement.
Tell Your Clinician Before Kidney Testing
Before a kidney test, tell the clinician or testing team that you use creatine. Share the product name, how much you take, when you started, and whether it contains other ingredients. Mentioning it before the result is interpreted can help the clinician decide whether a creatinine-based eGFR is enough or whether other tests or follow-up are appropriate.
Don’t stop or change a supplement solely to try to alter a test result without discussing it with your clinician. If you have kidney disease or receive an abnormal kidney test, ask how your creatine use affects the interpretation and what, if any, further assessment is needed. An elevated creatinine deserves context—not automatic reassurance and not an automatic conclusion of kidney damage.
