Why one marker does not tell the whole story
Creatinine is related to creatine metabolism, and many estimates of kidney filtration use a creatinine measurement. A factor that changes creatinine can therefore complicate a simple reading of an estimated filtration number. The clinical question is broader than whether a single result falls inside or outside the laboratory’s reference interval.
A clinician may interpret different markers and the pattern over time in light of the person’s circumstances. This is not a request for readers to choose or calculate their own diagnostic tests. It is a reason to tell the person ordering or reviewing the blood work about the exact supplement and use history. Keeping that information out of the conversation makes the result harder to interpret accurately.
What the 2025 review examined
Naeini and colleagues published a systematic review and meta-analysis on creatine supplementation and kidney function. The review included 21 studies. Twelve contributed to the pooled serum-creatinine analysis, and five contributed to the pooled filtration analysis. Those are different evidence sets, so the total count should not be used as though every study measured every outcome in the same way.
The full text reports a small increase in serum creatinine with supplementation and no statistically significant pooled difference in glomerular filtration rate. That pattern is relevant because a creatinine change does not necessarily imply the same change in measured kidney filtration. However, a nonsignificant pooled difference is not proof that harm is impossible for every person, dose, formulation or duration.
What the review cannot settle
The included research varied in design, participants, supplementation and follow-up. The authors report substantial variation in the creatinine findings and acknowledge that data beyond one year were sparse. Limited or inconsistent reporting also restricted some subgroup analyses. Those boundaries matter when someone tries to apply the overall conclusion to a particular medical condition or to years of unsupervised use.
The authors declared no competing interests. That is a useful transparency detail, but it does not erase the methodological limits or turn the review into a personal safety guarantee. Our reading used the published full text; we did not reanalyze its participant data. The source shelf identifies the paper and preserves the distinction between reading an analysis and independently reproducing it.
Healthy-adult guidance is not universal clearance
The NIH ODS exercise overview describes a generally reassuring safety record for creatine in healthy adults within the evidence it summarizes. That is a population and evidence statement, not a determination that a supplement is suitable for every reader. A person with known kidney disease, relevant medicines or an unexplained abnormal result needs individualized clinical advice.
The FDA also encourages consumers to discuss supplement use with a health professional. The fact that a powder is sold without a prescription does not establish that every use is appropriate or that its added ingredients are irrelevant. If you are comparing a plain powder with a blend, the serving-size guide explains why the whole label needs to come into the discussion.
Give the clinician the exact product details
Useful information includes the product name, ingredient list, labeled serving and what you have actually used. Include other supplements and medicines rather than treating the creatine tub in isolation. If the product has changed, mention the previous version too. A change in flavor, formula or serving directions can be relevant to understanding the exposure being discussed.
Do not conceal use or alter a routine just to make a laboratory number look different. Ask the clinician who ordered the testing how to handle the product and follow that guidance. This publication does not provide a stopping interval, a plan to restart or a threshold for declaring an abnormal value harmless. Those decisions require information an article does not have.
Product testing does not answer the kidney question
A certification can address contents, certain contaminants or sport-screening requirements. It is not a clinical evaluation of your kidney function. A powder can have an independently searchable testing record and still require a separate discussion about whether it fits your circumstances. The Thorne review is an example of a product record that should not be mistaken for individual medical clearance.
The same principle applies to a seller’s facility statement or a laboratory report. A document about a submitted sample does not predict how a particular person will respond. Our testing chapter explains those evidence categories so that a quality claim is neither dismissed nor given a medical meaning it does not carry.
Read reassuring evidence without overreading it
The 2025 findings help explain why creatinine and kidney filtration should not be treated as identical concepts in a supplement discussion. They support a more careful conversation, not a reflexive conclusion that every abnormal result is caused by creatine or that all kidney concerns have been resolved. The review’s different outcome sets, mixed studies and limited long-term data stay attached to its findings.
For the ingredient’s general exercise role, return to creatine monohydrate explained. For an actual result or symptom, take the question to a qualified clinician with the product details in hand. An educational guide can make that conversation more informed while leaving diagnosis and personal treatment decisions where the necessary clinical information is available.