What are the side effects of creatine (creatine monohydrate) supplementation?

From the Guidelines

Creatine supplementation is generally safe for most people when used as directed, but it can cause some side effects, particularly in individuals with pre-existing kidney conditions, as it may lead to rhabdomyolysis, a potential nephrotoxic effect, as noted in a study published in the American Journal of Kidney Diseases 1.

Common Side Effects

• Water retention, which may lead to weight gain of 1-2 pounds due to increased water content in muscles
• Digestive issues like stomach cramps, nausea, or diarrhea, especially when taking higher doses
• Dehydration can occur if adequate water intake isn't maintained while supplementing with creatine, so drinking plenty of water is essential
• Muscle cramps or strains may affect some individuals, though research on this is mixed

Special Considerations

• For those with pre-existing kidney conditions, caution is advised as creatine is processed by the kidneys, though studies in healthy individuals show no significant kidney damage from normal use, as seen in a case report where creatine supplementation did not alter kidney function in a patient with a solitary kidney 1
• The recommended dosage is typically 3-5 grams daily, with some people using a loading phase of 20 grams daily for 5-7 days before reducing to a maintenance dose
• To minimize side effects, start with a lower dose, stay well-hydrated, take creatine with meals, and consider using creatine monohydrate, which is the most researched and typically best-tolerated form

Monitoring and Precautions

• Monitor patients for elevated serum creatinine before every dose, especially when combining creatine supplementation with other medications or therapies that may affect kidney function, as recommended in the Journal of Clinical Oncology 1
• Assess for concomitant medications, prescribed and OTC, herbals, vitamins, nephrotoxic agents, or contrast media that may interact with creatine supplementation and affect kidney function.

From the Research

Creatine Supplementation Side Effects

• The most commonly reported side effects of creatine supplementation are gastrointestinal disturbances, such as diarrhea, stomach upset, and belching 2
• Muscle cramps have also been reported, although the evidence is largely anecdotal 3, 4
• Some studies have suggested that high doses of creatine supplementation may increase the risk of diarrhea 2
• There is no strong evidence to suggest that creatine supplementation has any detrimental effects on liver or kidney function in healthy individuals 3, 4
• The only consistently documented side effect of creatine supplementation is an increase in body mass 3, 4
• It is recommended that athletes take creatine under medical supervision and be educated on proper dosing to minimize the risk of side effects 4

Dose-Dependent Side Effects

• One study found that taking 10 grams of creatine per single serving increased the risk of diarrhea, while taking 5 grams per serving did not 2
• The risk of side effects may be increased with high doses of creatine supplementation, highlighting the importance of proper dosing and medical supervision 2, 4

Safety of Creatine Supplementation

• Overall, the evidence suggests that creatine supplementation is safe for healthy individuals when taken in recommended doses 3, 2, 4
• However, athletes should be aware of the potential for idiosyncratic effects and monitor their body's response to creatine supplementation 3