What Creatine Does: The Evidence and What Labels May Say

Creatine is a natural compound that your body makes and also takes in from food. In the United States, creatine supplements are sold as dietary supplements, which means they follow different rules from drugs. This guide explains what creatine is, what research reviews conclude, what US law lets a supplement label claim and what it does not, and the safety points that reviews raise. It is general information, not medical advice. Our guide to choosing a creatine supplement covers the buying checks.

What creatine is

According to the International Society of Sports Nutrition (ISSN) position stand of 2017, the majority of the body's creatine, about 95%, is held in skeletal muscle, and about half of the daily need is obtained from the diet. The same source puts the amount the body needs to replace at roughly 1 to 3 g a day and reports that vegetarians have lower muscle creatine stores on average. The 3 to 5 g a day used in research is somewhat more than that daily turnover.

What the research reviews conclude

The ISSN position stand concluded that creatine monohydrate is the most effective ergogenic (performance-enhancing) nutritional supplement currently available to athletes for increasing high-intensity exercise capacity and lean body mass during training, and the most extensively studied and clinically effective form. A 2024 follow-up by ISSN members (Part II) adds detail:

• Creatine alone may improve some measures of muscle performance, and people with lower starting stores, such as vegetarians and vegans, may respond more.
• In older adults, creatine alone has been linked to delayed fatigue and improved grip strength.
• Evidence in women is less extensive than in men, and research in female adolescent athletes is significantly lacking.

Most of this research is on creatine monohydrate, so it does not automatically carry over to other forms. Read the reviews with their funding in mind too: the 2017 position stand was prepared with support from the Council for Responsible Nutrition, a trade association for dietary supplement manufacturers, and several authors of the ISSN papers report roles with creatine manufacturers. We cite them next to the regulator sources below, and a society's position statement is not a claim a label may repeat.

What a US supplement label may claim

For structure/function claims, the United States does not keep a list of approved wordings. Health claims about reducing disease risk, which FDA either authorizes or, for qualified claims, allows under enforcement discretion, are a separate route. The law (21 U.S.C. 343(r)(6) and 21 CFR 101.93) lets a company make a "structure/function" claim, which describes an effect on the structure or function of the body, under conditions FDA lists on its notification page:

• The company must notify FDA no later than 30 days after first marketing the supplement with the claim.
• The company must have substantiation that the claim is truthful and not misleading, and the person who signs the notice certifies that it does.
• The label must show, prominently and in bold: "This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease."
• The claim may not say the product diagnoses, mitigates, treats, cures or prevents a specific disease or class of diseases.

The notice is not an approval request. FDA says it is not authorized to approve dietary supplements for safety and effectiveness before they are marketed. Some other countries keep registers of authorized claims with conditions of use, such as a daily amount; the US structure/function system has no such condition, so the amount behind a claim is the company's own choice. Wording about muscle strength, power or exercise performance is the kind of structure/function claim you will see around creatine. Wording about treating or preventing a named condition is a disease claim, and a supplement may not carry it as a structure/function claim.

How the FTC sees the claim

FDA's rules govern the label; the Federal Trade Commission (FTC) polices advertising, including listings and web pages. The FTC's health-products guidance says claims about health benefits and safety "require substantiation in the form of competent and reliable scientific evidence" and that randomized, controlled human clinical trials are the most reliable form of evidence. It says consumer experiences and anecdotes are never enough, that the disclaimer FDA requires "won't cure an otherwise deceptive ad," and that a testimonial being an honest opinion is not enough. Testimonials reporting results more dramatic than users can generally expect are likely to be deceptive.

How to check a claim on a label or listing

• Is the disclaimer there? A structure/function claim should come with the bold FDA statement quoted above.
• Does it promise to treat or prevent a disease? That is not allowed on a supplement. Treat the seller with caution.
• Do the form and amount match the research? The studies behind the reviews concern monohydrate at 3 to 5 g a day for maintenance. A claim for another form borrows that evidence unless the maker cites studies of that form; the 2022 Heliyon review says makers of alternative forms often cite studies of monohydrate or related ingredients to substantiate their products.
• Is the proof a testimonial or a before-and-after story? The FTC says anecdotes are never sufficient.
• Does the serving give a clear creatine amount? If a proprietary blend shows only a total weight, you cannot tell.

Safety: what the reviews say

The ISSN position stand concluded that there is no compelling scientific evidence that short- or long-term use of creatine monohydrate harms otherwise healthy people at the doses studied. The only consistently reported side effect is weight gain. A 2021 paper by ISSN members says a loading phase (about 20 g a day for 5 to 7 days) typically brings a 1 to 3 kg (2 to 7 lb) rise in body mass, mostly water, and also says creatine does not always lead to water retention. The same paper concluded that creatine does not cause dehydration or muscle cramping, and noted that no study has reported hair loss in humans, although one small study of rugby players found a rise in the hormone DHT that has not been replicated. A 2025 review in Frontiers in Nutrition, whose publication fee was paid by the creatine maker Alzchem and one of whose authors reports serving on Alzchem's scientific advisory board, found no adverse effects on kidney function in healthy people, no significant effects on hydration or thermoregulation, and no support for a link to cancer. It reports stomach upset, particularly at high doses, which is dose-related. These conclusions concern healthy adults; they are not advice for anyone with a medical condition.

Who should ask first

• People with kidney disease. The ISSN suggests consulting a physician. The 2025 review advises caution, and the AAOS patient site says people with kidney problems should never take creatine supplements. Creatine can also affect the blood creatinine readings used to judge kidney function, so tell your clinician you take it.
• People who are pregnant or nursing. FDA advises discussing any supplement with your provider, and the 2025 review says that, with human evidence limited, creatine should not be recommended in clinical practice outside research.
• People who take prescribed medicines. FDA says certain supplements can change how a medicine is absorbed, metabolized or excreted.
• People under 18. Expert views differ, as our buying guide sets out. Ask a doctor first.
• Athletes who are drug tested. USADA says you always assume some risk of testing positive when you use supplements.

Using this when you shop

Check that the creatine per serving is stated, that any claim comes with the FDA disclaimer and does not promise to treat a condition, and that the label shows directions and warnings. Searches such as creatine monohydrate powder on Amazon (opens in a new tab) and creatine monohydrate Creapure on Amazon (opens in a new tab) show many listings, and the label on the pack, not the listing, is what counts.

For how much to take and when, see how to take creatine. Your doctor or pharmacist is the right person to ask if you have a health condition or take medicines, and the label is the authority on dose and warnings.