Creatine: Dangers, Side Effects and Contraindications, According to Studies

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Creapure Creatine

Creatine monohydrate Creapure in vegetable capsules (HPMC). Three capsules daily provide 3 g of creatine monohydrate, with a large glass of water, preferably 1 to 2 capsules after exercise.

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In 2025, a team reviewed the 685 clinical trials published on creatine in humans, 95% using monohydrate, at approximately 12.5 g per day on average for 64.7 days, and up to 14 years for the longest studies.

Limitation acknowledged by the authors: the analysis depends on what each trial published, and some poorly detailed their adverse effects. Among 28.4 million adverse event reports, creatine appears in 0.00072% of cases, most often with another form of creatine or other products.

Long-term trials point in the same direction. In 175 patients with amyotrophic lateral sclerosis, 10 g per day for an average of 310 days did not significantly increase nausea (23% versus 24% with placebo) or diarrhea (35% versus 24%), but three patients discontinued due to severe digestive problems that resolved upon stopping. In 1,741 patients with Parkinson's disease, 10 g per day with a median follow-up of 4 years (up to 8 years) showed no detectable difference in adverse effects, serious or otherwise. According to the International Society of Sports Nutrition, in 2017, the only consistently reported adverse effect is weight gain.

Creatine enters muscle via a transporter that works with sodium, and water follows. A loading phase of 20 g per day for 5 to 7 days typically results in 1 to 3 kilos of weight gain, mostly from water, according to a 2021 review; the International Society of Sports Nutrition's position mentions temporary retention of 0.5 to 1 liter.

Over time, the gain combines water and muscle. A meta-analysis of 61 trials combining creatine and resistance training, published in 2025, finds +0.89 kilo of body weight (95% confidence interval 0.76 to 1.01) and +1.39 kilo of lean mass, with no significant effect on fat mass. In women, a 2020 meta-analysis finds no significant difference in weight gain between creatine and placebo.

In the trial of 175 patients mentioned above, limb edema was observed more often with creatine after two months, likely related to water retention. Without danger, this gain matters in weight-class sports: better to start well before weigh-in, without a loading phase.

These are the most frequently reported adverse effects. A high dose taken all at once is not fully absorbed, and the creatine remaining in the intestine draws water there: the risk therefore depends mainly on the dose per intake.

The placebo figure reminds us that these symptoms are common in athletes. A 2025 review concludes that digestive disorders are generally mild and infrequent, mainly linked to doses exceeding 10 g, and recommends dividing doses into 5 g maximum per dose.

Our two creatine supplements remain within these amounts per dose. The Creapure Creatine is taken at 3 capsules per day, or 3 g, with a large glass of water, with 1 to 2 capsules preferably after exercise. The Creatine monohydrate powder is dosed at 5 g per day, approximately one measuring spoon, in a glass of water, juice, or shaker. Taking it with a meal is a practical trick for sensitive stomachs, without dedicated trial data.

The concern arose in the late 1990s from a published case, detailed below. Since then, trials have measured renal filtration by 51Cr-EDTA clearance, a reference method that does not rely on creatinine.

Two meta-analyses published in 2026 provide an update. The first (20 trials) found +0.13 mg/dL blood creatinine, with no difference for urea or estimated glomerular filtration rate (−5.20 mL/min/1.73 m², range −15.00 to 4.60), whether supplementation lasted less or more than one month. The second (26 studies, 1,036 healthy participants or those with chronic kidney disease) found +0.14 mg/dL creatinine and creatinine-estimated glomerular filtration rate lowered by 10.75 mL/min, but no significant difference for filtration measured by 51Cr-EDTA (+5.89 mL/min, range −0.30 to 12.08): according to its authors, an effect on creatinine metabolism rather than kidney damage.

These 26 practitioners derived their protein from their usual diet; the trial says nothing about protein powders. For those supplementing their intake, our Whey 100% Isolate provides 22.9 g of protein per 30 g serving, and our guide on whey reviews its effects.

Creatinine is a waste product from the spontaneous breakdown of muscle creatine, approximately 2% per day according to a 2025 review, then eliminated by the kidneys. Its level is used to estimate renal filtration, but it also depends on muscle mass and creatine intake: under creatine supplementation, the calculation may conclude a lower filtration than actually exists.

In the 2008 trial of 18 sedentary men, creatinine decreased with training under placebo but not under creatine, whereas cystatin C, a marker independent of creatine, decreased in both groups. In 2014, a case was published of a man taking creatine ethyl ester, another form than monohydrate: his creatinine suggested advanced kidney failure, but kidney function proved normal and abnormalities disappeared upon discontinuation. The authors spoke of false kidney failure.

The case that launched the controversy, published in 1998, involved a young man who had suffered for 8 years from a kidney disease, segmental and focal hyalinosis with relapsing nephrotic syndrome, treated with cyclosporine, an immunosuppressant. After 15 g of creatine per day for 7 days then 2 g per day for 7 weeks, his creatinine had increased; he was advised to stop. According to a 2021 review, other published cases involved medications, preexisting kidney disease, other supplements, doses up to 100 times too high, or anabolic steroids, without an established causal link.

In persons already with kidney disease, data are scarce. In a small trial of 10 hemodialysis patients divided between creatine and placebo, creatine before each session for 4 weeks reduced cramps by 60%, with no adverse effects, and a slight increase in creatinine (from 10.7 to 12.4 mg/dL). A Brazilian team observed no kidney damage in a young man with a single kidney and mild kidney failure. This is encouraging, but too thin to conclude.

The International Society of Sports Nutrition mentions, as a precaution, medical advice in case of preexisting kidney disease; a 2006 review then advises against creatine. A 2025 review recommends close monitoring if kidney function is reduced or at risk, and recalls that an earlier review cited diabetes, hypertension, or reduced filtration.

Diabetes deserves separate mention: in 25 type 2 diabetic patients on an exercise program, 5 g of creatine per day for 12 weeks lowered hemoglobin A1c from 7.4 to 6.4%, versus 7.5 to 7.6% under placebo, with comparable adverse effects. On treatment that lowers blood glucose, inform your doctor: the interaction has not been studied, but it is plausible.

The idea: by drawing water into muscle, creatine would deprive the rest of the body. Surveys fueled it: 34 of 90 athlete users (38%) reported negative effects, mainly cramps; among 52 college players, 25% reported cramps and 13.5% dehydration symptoms. These surveys controlled neither doses nor other supplements; in one, 91% of users exceeded 5 g per day in maintenance.

Controlled trials say otherwise. In 72 American football players followed for a season, at 27°C and 54% humidity on average, the 38 taking creatine (0.3 g per kilo per day for 5 days, then 0.03 g per kilo) had significantly fewer cramps, heat-related disorders or dehydration and muscle tears than the other 34; however, players self-selected their group. In trained men dehydrated by 2% and exercising in heat, 21.6 g per day for 7 days did not impair hydration or thermoregulation.

Across the 685 trials, the difference in cramps or pain per participant was not significant (0.52% versus 0.07%). One isolated signal exists: in 14 students, a dose of 0.3 g per kilogram per day for 6 days, then 0.03 g per kilogram, increased pressure in the anterior compartment of the leg by 76% at rest compared to placebo, and by 72% at 34 days. The trial measured pressure, not compartment syndromes, but intense and worsening leg pain during exercise requires stopping and medical consultation.

Our two creatine products remind you to maintain adequate hydration. For other causes of cramps, see our guide cramps: causes and solutions.

The rumor is based on a single trial and a real mechanism: dihydrotestosterone, or DHT, derived from testosterone, can shrink sensitive hair follicles and contributes to male baldness.

Hair was not examined. A 2021 review emphasizes that DHT remained within normal ranges, that the creatine group started with DHT 23% lower, and that the result has never been replicated. Of 12 other studies measuring testosterone under creatine, 10 found no change and 2 found a slight increase.

This trial has its limitations: 12 weeks, men only, no loading phase and no record of family history, which matters, since according to the authors a man whose father lost his hair has twice the risk of losing his. See our guide on hair loss.

Liver. In footballers followed for 21 months as in women (2020 meta-analysis), liver markers did not differ significantly under creatine. Two cases are published. A 27-year-old weight training enthusiast, on creatine for 8 to 9 months and whey for 4 weeks, presented with jaundice from cholestatic liver damage, improved after infusion and discontinuation of supplements. In 2026, a 23-year-old man developed severe rhabdomyolysis (creatine kinase beyond 120,000 U/L, elevated liver enzymes) after more than 4 hours of weight training, on multiple supplements including 5 g of creatine; his condition improved in 10 days, without acute kidney failure. These cases combine multiple products or extreme exertion, with no established responsibility of creatine alone.

Heart and blood pressure. In 2005, a case of atrial fibrillation was published in a 30-year-old man on creatine monohydrate, with no established causal link. Controlled data are reassuring: 10 to 20 g per day for 5 to 31 days did not change blood pressure in young adults, and in a two-year trial in postmenopausal women, at 0.14 g per kilogram per day, blood pressure did not evolve differently under creatine (60 women) and under placebo (52). No study has been conducted in people already hypertensive.

Mood and bipolar disorder. This is the most serious signal in this section. In a small open trial in 10 patients with treatment-resistant depression, at 3 to 5 g per day for 4 weeks, the two patients with bipolar disorder presented with an episode of hypomania or mania.

Four switches in 19 bipolar patients exposed, in two small studies: a signal sufficient to not take creatine in this case without discussing it with your psychiatrist. The effects studied on the brain are detailed in our article creatine and brain.

Cancer. The concern comes from heterocyclic amines, carcinogenic compounds formed when meat is cooked at high temperature. In young adults, 7 g of creatine per day for 7 days then 5 g maximum for 23 days did not increase these compounds. A mouse study associated creatine with more liver metastases, but at a dose equivalent to approximately 28 g per day in humans. A 2025 review concludes that nothing shows that 3 to 5 g per day increases cancer risk in humans.

Adolescents. In a survey, 21% of male high school students and 3% of female high school students reported taking creatine. According to a 2021 review, trials in adolescent athletes consistently report an absence of adverse effects, but another review notes that these performance trials did not measure health markers. In adolescent girls with treatment-resistant depression, 2, 4, or 10 g per day for 8 weeks did not cause more adverse effects, weight gain, or increased creatinine than placebo. Due to the lack of long-term trials, our creatines are not recommended for children and adolescents, and medical advice is required before age 18.

Pregnancy. In animals, maternal creatine protected newborns from oxygen deprivation, with no observed adverse effects. In pregnant women, there are no randomized trials on its safety, and initial tolerance studies are underway. In 951 women aged 16 to 67, outside of pregnancy, a meta-analysis of 29 studies found neither serious adverse effects nor an excess of adverse effects (relative risk of 1.24, 95% CI 0.51 to 2.98). A 2025 review concludes that it should not be recommended during pregnancy outside of research settings.

Breastfeeding. We identified no supplementation trials during breastfeeding. Our two creatines are not recommended for pregnant or breastfeeding women; outside these periods, our article on creatine for women details the studies.

The classic loading phase, approximately 20 g per day in 4 doses of 5 g for 5 to 7 days, quickly fills muscle stores, but causes 1 to 3 kg weight gain in a few days. It is not essential. In a landmark trial of 31 men distributed across several protocols, 20 g per day for 6 days increased muscle creatine by approximately 20%, and 3 g per day for 28 days resulted in comparable increase, approximately 20%, more gradually. The position of the International Society of Sports Nutrition recommends 3 to 5 g per day for maintenance.

A 2021 review presents the daily dose as the option for those wanting to avoid rapid weight gain and recommends, in case of loading, doses of 10 g at most.

The 1996 trial involved 3 g of creatine per day for 28 days, measured in muscle; it tested neither capsules nor our product. Our Creapure Creatine provides 3 g of creatine monohydrate per day, in 3 vegetable capsules. Our Creatine monohydrate powder is dosed at 5 g per day, approximately one measuring scoop, which is the upper end of the maintenance range. See also our comparison creatine powder or capsules and our guide when to take creatine.

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Creatine monohydrate powder

100% creatine monohydrate powder. 5 g per day, approximately one measuring scoop, in a glass of water, juice, or shaker, preferably after exercise or anytime on rest days.

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The most concrete risk does not always come from creatine itself. A 2006 review estimated that the main health risk likely came from the purity of commercial creatines. A Brazilian method development study published in 2025 classified 117 of its 149 samples as pure by chromatography and 32 as adulterated; the abstract does not specify their origin or the nature of the adulteration. Manufacturing by-products, such as dicyandiamide or dihydrotriazines, are also suspected of causing digestive issues in sensitive individuals, a matter of purity rather than creatine according to the 2025 review.

These analyses describe neither a specific market nor a particular product. For tested athletes, our guide on doping and banned substances details the risk of supplement contamination.

The rules below are practical advice drawn from this data.

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