What are the side effects of taking creatine and how can they be managed?

Side Effects of Creatine Supplementation

Creatine supplementation is generally well-tolerated with minimal side effects when used at recommended doses (loading: 20g/day for 5-7 days; maintenance: 2-5g/day), with the most common effect being transient water retention and weight gain of 1-2 kg. 1, 2

Common and Expected Effects

Weight Gain and Water Retention

• The expected effect of creatine supplementation is a 1-2 kg body mass increase due to intracellular water retention, which is a physiological response rather than a true adverse effect 1
• This weight gain occurs early in supplementation and is generally well-tolerated by users 2

Gastrointestinal Effects

• Gastrointestinal disturbances have been reported occasionally, though these effects are largely anecdotal 3
• Diarrhea has been documented as a potential side effect, particularly with higher doses 4

Musculoskeletal Complaints

• Muscle cramps have been reported occasionally in healthy individuals, though the evidence is anecdotal 3
• Cramping may be related to dehydration or electrolyte imbalances rather than direct creatine toxicity 4

Renal Considerations

Safety in Healthy Individuals

• Short-term (5 days), medium-term (9 weeks), and long-term (up to 5 years) creatine supplementation has not shown adverse effects on renal function in healthy individuals when monitored by clearance methods and urine protein excretion 3
• Creatine supplementation appears safe when used by healthy adults at recommended loading (20g/day for 5 days) and maintenance doses (≤3g/day) 5

Renal Dysfunction Risk

• In patients with pre-existing renal disease or those taking nephrotoxic medications, creatine may be associated with increased risk of renal dysfunction 5
• One case report documented acute renal failure in a 20-year-old man taking 20g/day for four weeks, though this represents an isolated case 5
• If a patient taking creatine develops evidence of renal dysfunction, it is necessary to discontinue this supplement 6

Monitoring Considerations

• Creatine supplementation may increase serum creatinine levels, which can act as a false indicator of renal dysfunction 5
• This confounding effect makes it important to use additional renal function markers beyond serum creatinine when monitoring patients on creatine 5

Hepatic Safety

• Medium-term (4 weeks) creatine supplementation in young athletes showed no evidence of liver dysfunction based on serum enzymes and urea production 3
• When combined with other supplements or taken at higher than recommended doses for several months, there have been isolated cases of liver complications 2

Other Reported Effects

Neurological and Systemic

• Dizziness has been reported as a potential side effect 4
• Dehydration has been linked to creatine use, though the mechanism is unclear 4

Metabolic Concerns

• Possible influence on insulin production has been suggested but not well-established 7
• Potential feedback inhibition of endogenous creatine synthesis with prolonged use 7

Dosing and Safety Recommendations

Standard Dosing Protocol

• Loading dose: 20g/day divided into four equal doses for 5-7 days, followed by maintenance dose of 3-5g/day 1
• Alternative approach: 0.3 g/kg/day for 5-7 days loading, then 0.03 g/kg/day maintenance for 4-6 weeks 2

Conservative Approach

• In healthy subjects with recreational sport participation, oral creatine supplementation should be less than 2.5-3g per day (approximately the daily turnover rate) 7
• In athletes with high-intensity training, maximal supplementation should be less than 5-6g per day for less than two weeks under medical supervision 7
• Oral administration of more than 6g per day should be considered a therapeutic intervention and prescribed by physicians only in cases of suspected deficiency or severe stress/injury 7

Product Quality Concerns

Contamination Risk

• During industrial production from sarcosine and cyanamide, variable amounts of contaminants (dicyandiamide, dihydrotriazines, creatinine, ions) are generated 7
• Because sarcosine could originate from bovine tissues, risk of prion contamination from bovine spongiform encephalopathy cannot be excluded 7
• Commercially marketed creatine products do not meet the same quality control standards as pharmaceuticals, raising concerns about impurities or inaccurate dosing 4

Special Populations

Pediatric Use

• The safety of creatine in children and adolescents has not been established 5
• Despite lack of safety data, creatine use has spread to children and adolescents 4

Long-Term Use

• Few trials investigate long-term use exceeding 10g/day 5
• Further studies are needed to evaluate remote and potential future adverse effects from prolonged supplementation 2

Clinical Monitoring Recommendations

• Regular monitoring is compulsory to avoid abnormal reactions during oral creatine supplementation 3
• When monitoring renal function, use markers beyond serum creatinine and creatinine clearance to avoid false indicators of dysfunction 5
• Idiosyncratic effects may occur when large amounts are consumed, increasing the load on liver and kidneys 3