Creatine side effects

Short answer

According to the ISSN, the only side effect consistently reported in the literature for creatine monohydrate is weight gain; claims about kidney, liver, cramps and dehydration were not confirmed in controlled studies, while digestive complaints were associated with high amounts taken at one time during loading. Important limits: most of the evidence comes from young, healthy adults; studies in people with chronic kidney disease are insufficient; product content may vary by manufacturer. ^{[1] [5] [2]}

What are the known side effects of creatine?

The ISSN 2017 paper states that more than 1,000 studies have been done since creatine monohydrate became widespread in the early 1990s and that the only side effect consistently reported in the literature is weight gain. The same paper says that studies lasting up to 5 years, at doses of 0.3–0.8 g/kg per day, in healthy and patient groups ranging from infants to older adults, show that creatine poses no health risk. ^[1] The IOC’s 2018 consensus statement states that no adverse health effects were reported with long-term use up to 4 years when appropriate loading protocols were followed, that a body weight gain of 1–2 kg (mainly due to water retention) may be seen after loading, and that this may be a disadvantage for endurance performance, sports in which body weight is carried against gravity (for example, high jump), or sports with a specific weight target. ^[8]

These views have a limit: the ISSN 2017 paper was supported by the supplement industry’s trade association, and many of the authors have ties to companies selling creatine; one of the authors of the ISSN 2021 paper is also an ISSN executive, and the ISSN receives support from companies that produce and sell creatine. ^{[1] [2]} For this reason, in the sections below each claim is given together with its own study.

Does creatine harm the kidneys?

What did controlled studies show?

In the randomized, double-blind, placebo-controlled study by Lugaresi and colleagues, healthy people performing resistance training and eating a high-protein diet (≥1.2 g/kg/day) received for 12 weeks either 20 g per day for 5 days followed by 5 g per day of creatine, or placebo. Glomerular filtration rate was measured directly by chromium-51 EDTA clearance: it changed from 101.42 ± 13.11 to 108.78 ± 14.41 mL/min/1.73 m² in the creatine group and from 103.29 ± 17.64 to 106.68 ± 16.05 in the placebo group; the group × time interaction was not significant (p = 0.64). Creatinine clearance, urea, electrolytes, proteinuria and albuminuria also practically did not change. ^[4]

In the 2003 study by Kreider and colleagues, 98 Division I collegiate football players were followed open-label for 21 months; those receiving creatine took 15.75 g per day for 5 days, followed by an average of 5 g per day (with doses of 5–10 g). In a 69-item blood and urine panel (kidney function, liver and muscle enzymes, electrolytes, lipids and others), no clinically significant difference was found between groups. This study is open-label, randomization was not reported, and it covers young male athletes. ^[3]

The ISSN 2017 paper also relays that use of 20 g per day for 5 days and up to 10 g per day for 10 months to 5 years (Poortmans and colleagues) did not affect creatinine clearance and glomerular filtration, that 12 weeks of use in people with type 2 diabetes did not impair kidney function, and it concludes that “there is no compelling evidence that creatine negatively affects kidney function in healthy or patient populations”; it relays the view that people with pre-existing kidney disease should consult a physician as a precaution not as its own recommendation but as the view of some authors. ^[1]

The 2023 narrative review (Longobardi et al.) concludes that although a few case reports and animal studies suggested that creatine may impair kidney function, controlled clinical studies do not support this claim; based on studies measuring kidney function with reliable methods, it states that creatine supplements are safe for human consumption. The same review stresses that studies are still needed in people with pre-existing kidney disease. ^[5]

Why are case reports not considered reliable?

The ISSN 2021 paper relays that the association between creatine and kidney damage rests on a single case reported in 1998: a young man who had had focal segmental glomerulosclerosis and relapsing nephrotic syndrome for eight years and had been using cyclosporine (an immunosuppressant) for five years had newly started creatine, his blood creatinine level rose, and judging from calculated creatinine clearance, his kidney status was thought to have worsened. The paper states that the maintenance amount used was close to the creatine a typical omnivore takes in through food, that it was already known that creatinine levels may rise with food and supplements, and that two separate teams of experts wrote letters to The Lancet. It also states that the small number of case reports compiled later were confounded by medications, pre-existing kidney disease, concurrent other supplements, inappropriate dose (such as about 100 times the recommended) and use of anabolic androgenic steroids. ^[2]

Why does creatinine come out high when creatine is used?

Creatine and phosphocreatine convert non-enzymatically to creatinine in muscle; creatinine passes into the blood and is excreted in urine. Blood creatinine level depends on muscle mass and on creatine and creatinine taken in through food; it is higher in men than in women. Creatine supplementation and meat consumption can raise blood and urine creatinine. ^[2] Longobardi and colleagues also state that creatine can raise serum creatinine in some people, but that because creatine converts to creatinine spontaneously, this does not necessarily indicate kidney dysfunction. ^[5]

According to the review by Persky and Rawson (relayed by ISSN 2021), in 12 of the creatine studies serum creatinine did not rise, in 8 the rise stayed within the normal range, and in only 2 did it exceed normal limits (in one it did not differ from the control group). The ISSN 2021 paper states that care is needed when using blood creatinine and estimated creatinine clearance/glomerular filtration rate in people who eat a lot of meat or use creatine. ^[2] For this reason, in interpreting a creatinine-based kidney test, knowing about creatine use affects the meaning of the result.

Does creatine harm the liver?

In the 21-month follow-up by Kreider and colleagues, in a 69-item panel including muscle and liver enzymes, no clinically significant difference was found between those who took creatine and those who did not. ^[3] This finding comes from an open-label follow-up in young male football players; it provides no data for people with liver disease.

Does creatine cause water retention or weight gain?

The ISSN 2021 paper states that the most common side effect of creatine is water retention in the first days, but that this short-term response has been generalized to the long term; in some of the 5–10-week studies, total body water did not increase significantly (for example, in trained men who took 0.3 g/kg lean mass/day for 7 days followed by 0.075 g/kg for 28 days). ^[2] According to the IOC, a 1–2 kg increase can be expected after loading, and this is mainly due to water retention. ^[8]

Does creatine cause muscle cramps and dehydration?

In the systematic review by Lopez and colleagues, 15 of 95 articles had examined the effect of creatine on thermoregulation or hydration; two independent reviewers selected 10 studies (PEDro score 7–10). Result: there was no evidence that creatine supplementation impairs the body’s ability to dissipate heat or adversely affects fluid balance; in controlled studies with athletes exercising in the heat, no adverse effect was seen at recommended doses. ^[6] The ISSN 2017 paper also relays studies in which the incidence of cramps, heat illness/dehydration, muscle tightness and muscle strain was reported to be lower in collegiate football players taking creatine than in those not taking it. ^[1] The ISSN paper relays these comparisons without specifying randomization; the findings do not prove that creatine prevents cramps, but they are also inconsistent with the claim that it increases cramps.

Does creatine cause digestive problems?

The ISSN 2021 paper states that single servings above 10 g during loading may cause diarrhea. ^[2] In the 28-day double-blind study of 59 elite male soccer players by Ostojic and Ahmetovic, the diarrhea rate was 28.6% in those taking 2 × 5 g per day, 55.6% in those taking 10 g once daily, and 35.0% in the placebo group; the 5 g split dose could not be distinguished from placebo, while the single 10 g dose differed significantly from the placebo and 5 g groups. The data rest on a complaint questionnaire. ^[7]

Is there a risk of contamination and banned substances in creatine products?

Apart from creatine itself, the purity of the product is a safety matter. The ISSN 2021 paper relays that in some creatine monohydrate sources produced with different starting materials and synthesis methods, up to 5.4% dicyandiamide, 0.09% dihydrotriazine, 1.3% creatinine, dimethyl sulfate, thiourea and/or heavy metals such as mercury and lead were detected; it states that the health effects of these compounds are unknown and that dihydrotriazine raises the most concern because of its structural similarity to carcinogenic compounds. ^[2]

For athletes there is a separate risk: the IOC paper states that inadvertent intake of banned substances in supplements is a known risk, that even very small amounts of banned-substance contamination can lead to a positive doping test, and that third-party testing programs help manage the risk but no absolute guarantee exists for any product. ^[8]

Who should be especially careful?

• Chronic kidney disease: Few studies have been done in this group; the 2023 review says additional studies are needed, and the ISSN also relays the view that a physician should be consulted as a precaution. ^{[1] [5]}
• People using medication: The patient in the 1998 case report was using an immunosuppressant (cyclosporine), and medications were among the confounders in later reports as well; this means individual medication review is needed. ^[2]
• Pregnant and breastfeeding women: It is stated that no human study evaluating creatine supplementation in pregnancy exists. ^[2]
• Under 18: The ISSN argues that age warnings on labels are a legal precaution and that use is conditionally acceptable; this is the view of an association. ^[1]

Detailed guideCreatine: overview, safety and evidence summary→ Detailed guideCreatine benefits: which claims are supported?→ Detailed guideHow is creatine used? Protocols applied in studies→ Detailed guideCreatine monohydrate and other forms→

This guide does not recommend a personal dose or product.

What did the 2025 hair study add?

In a double-blind trial, 45 resistance-trained men were assigned to creatine or placebo and 38 completed follow-up. After 12 weeks, changes in hair density, thickness and DHT did not differ between groups. This is more direct evidence than the hormone-only 2009 study. One short trial cannot settle long-term risk or outcomes in women, but it is no longer accurate to say that hair outcomes have never been studied. ^[9]