Creatine Side Effects: What Research Actually Shows

Creatine is one of the most rigorously studied nutritional supplements in exercise and sport science. It is a nitrogenous organic acid derived from glycine, L-arginine, and S-adenosyl-L-methionine, involved in energy transfer through the phosphocreatine (PCr) system. More than 95% of the body's total Creatine is located in skeletal muscle and brain, where it plays a critical role in rapidly regenerating ATP — the cell's primary energy currency.

Given Creatine's widespread use among athletes, active individuals, and older adults seeking to support muscle strength, recovery, and cognitive function, questions about Creatine side effects are among the most commonly searched topics in sports nutrition. Understanding what the clinical research actually shows — rather than relying on anecdote — is essential for making informed decisions.

Available literature consistently shows that Creatine monohydrate is safe when taken at recommended doses, even in clinical populations. However, specific concerns have been raised over the years regarding kidney function, gastrointestinal comfort, and other potential effects. Below, we examine each of these areas using findings from controlled clinical trials and systematic reviews.

The most persistent concern regarding Creatine side effects involves kidney health. This worry originated in the late 1990s, driven by case studies and preclinical trials in animal models. However, most of these reports rely on retrospective observational data from individuals with pre-existing kidney conditions, who engaged in high-intensity or high-volume exercise, and/or who used other substances known to affect renal function.

Despite a few case reports and animal studies suggesting Creatine may impair kidney function, clinical trials with controlled designs do not support this claim. Researcher Poortmans conducted studies showing that short-term supplementation does not alter glomerular filtration rate and that chronic supplementation of up to five years' duration did not impair renal function in healthy athletes.

A randomized, double-blind, placebo-controlled trial tested the renal effects of high-dose Creatine supplementation at 10 grams per day for 3 months. The authors concluded that high-dose daily Creatine supplementation for 90 days does not provoke renal dysfunction. Published studies have investigated the effects of Creatine monohydrate supplementation from 5 to 20 g/day for up to 24 months on renal function in various populations, with results consistently showing no adverse effects in healthy individuals.

The Serum Creatinine Confound

Creatine supplementation may increase serum creatinine concentration for some individuals, but this does not necessarily indicate kidney dysfunction. Creatine is spontaneously converted into creatinine in the body, so elevated serum creatinine may reflect exogenous Creatine intake rather than renal pathology. In RCT data, the increases observed (0.1–0.2 mg/dL) were well within normal values for active individuals. Clinicians interpreting kidney function markers in Creatine users should be aware of this diagnostic confound.

Important caveat: Animal studies have indicated that Creatine could potentially exacerbate renal deterioration in pre-existing kidney conditions. Individuals with known renal disease should not use Creatine supplements without medical supervision. Caution is also advised for pregnant women, as evidence is lacking for these populations.

Gastrointestinal Discomfort

Gastrointestinal discomfort — including bloating, cramping, and diarrhea — has been anecdotally reported among Creatine side effects, particularly with large loading doses. In published RCT data comparing buffered Creatine to standard Creatine monohydrate, no side effects were reported. Taking Creatine with food and adequate hydration is commonly practiced by study participants and may help minimize GI issues.

Carcinogenicity Concerns

Although some theoretical risks — such as Creatine's potential to form carcinogenic compounds — have been discussed in the scientific literature, the available research does not support a link between Creatine supplementation and cancer.

Product Purity and Impurities

Like other dietary supplements, Creatine products may contain heavy metals such as lead, arsenic, and mercury. Impurities such as creatinine, dicyandiamide, and heavy metals can appear in poorly manufactured products. Third-party certification (e.g., NSF, Informed-Sport, USP) provides additional assurance of product purity and is an important consideration when selecting a Creatine supplement.

Creatine remains one of the most popular and well-researched supplements in the world because its benefits are supported by extensive clinical evidence. Research suggests it supports athletic performance, muscle recovery, energy production, and even cognitive function — making it relevant for a broad range of individuals.

Studies suggest Creatine supplementation increases intramuscular phosphocreatine stores, facilitating a greater capacity to rapidly resynthesize ATP during high-intensity exercise. A 2025 network meta-analysis comparing Creatine, protein, and omega-3 supplementation across 35 randomized controlled trials found that Creatine demonstrated superior effects for muscle strength (SMD = 0.46, 95% CI: 0.29 to 0.63).

Research also suggests Creatine may support cognitive function. Current evidence indicates that Creatine monohydrate supplementation may confer beneficial effects on memory, attention time, and information processing speed in adults. It has been shown to improve measures of cognition and memory, primarily in aging adults and during times of metabolic stress such as sleep deprivation.

Meta-analyses confirm it may attenuate exercise-induced Creatine kinase elevation and reduce force-production loss post-exercise. A 2025 double-blind RCT found Creatine accelerated recovery of muscle function, reduced stiffness, and decreased fatigue after eccentric exercise. For older adults, accumulating evidence indicates that Creatine supplementation combined with resistance training may have anti-sarcopenic effects, increasing aging muscle mass and upper- and lower-body strength.

As a dietary supplement take 5g (approximately 1 scoop) daily, or as directed by your healthcare practitioner.

Each container provides 90 scoops. This product is gluten free and soy free.

Taking Creatine with food and adequate hydration is commonly practiced by study participants and may help minimize any gastrointestinal discomfort that has been anecdotally associated with Creatine use.