Creatine Side Effects and What the Evidence Says

Creatine is among the most studied sports supplements, and the safety literature is correspondingly substantial. This page summarises what that literature addresses and where genuine caution applies.

Kidney function

This is the most frequently raised concern. Creatine supplementation raises blood creatinine, which is a marker commonly used to estimate kidney function — meaning a routine blood test can show a changed value that reflects supplementation rather than kidney damage. If you use creatine, tell the clinician ordering the test.

The ISSN position stand addresses kidney safety in healthy individuals directly. That evidence concerns healthy adults, and it does not extend to people with existing kidney disease. If you have any kidney condition, or take medication affecting the kidneys, speak to your doctor before using creatine.

Digestive effects

Stomach discomfort is reported most often at higher intakes and with large single servings — see loading and water retention.

Hair loss

This question traces to a single small study and has been discussed extensively since. It is an area where the honest position is that the evidence is limited rather than settled in either direction, and where any site telling you confidently that the question is closed is overstating what exists.

Product quality

Creatine is a bulk ingredient and quality varies between suppliers. Third-party certification — Informed Sport, NSF Certified for Sport — is meaningful here, particularly for anyone subject to drug testing, where contamination of a supplement is the risk being managed. Where a manufacturer states a certification we record it as their claim; we have not verified it.

Who should not use creatine without medical advice

• Anyone with kidney or liver disease
• Anyone taking regular prescription medication, particularly nephrotoxic drugs or NSAIDs at high doses
• People who are pregnant or breastfeeding
• Under-18s

Please read our medical disclaimer. This page is consumer information, not medical advice.

References

• NIH Office of Dietary Supplements — Dietary Supplements for Exercise and Athletic Performance
• International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation