Merck Manual

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Laura Shane-McWhorter

, PharmD, University of Utah College of Pharmacy

Last full review/revision Jul 2020| Content last modified Jul 2020
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Phosphocreatine is a compound stored in muscle; it donates phosphate to ADP and thereby rapidly replenishes ATP during anaerobic muscle contraction. It is synthesized endogenously in the liver from arginine, glycine, and methionine. Dietary sources are milk, steak, and some fish.


Creatine is said to improve physical and athletic performance and to reduce muscle fatigue.


Some evidence suggests creatine is effective at increasing work done in a short duration, maximal effort (eg, sprinting, rowing, weightlifting). It has proven therapeutic use in muscle phosphorylase deficiency (glycogen storage disease type V [McArdle disease]) and gyrate atrophy of the choroid and retina; early data also suggest possible effects in Parkinson disease and amyotrophic lateral sclerosis.

Numerous clinical trials have demonstrated that creatine supplementation is well tolerated and may increase muscle mass. The effects can be seen in normal healthy people as well as a means of aiding in the treatment of muscle disorders and improving physical function and quality of life in patients with muscle disorders or osteoarthritis (1-3).

Adverse effects

Creatine may cause weight gain (possibly because of an increase in muscle mass) and spurious increases in serum creatinine levels. Minor gastrointestinal symptoms, dehydration, electrolyte imbalance, and muscle cramps have been reported anecdotally.

Drug interactions

None are well documented.

Creatine references

  • Kley RA, Tarnopolsky MA, Vorgerd M: Creatine for treating muscle disorders. Cochrane Database Syst Rev(6):CD004760, 2013. doi: 10.1002/14651858.CD004760.pub4.

  • Branch JD: Effect of creatine supplementation on body composition and performance: a meta-analysis. Int J Sport Nutr Exerc Metab 13(2):198-226, 2003.

  • Neves M Jr, Gualano B, Roschel H, et al: Beneficial effect of creatine supplementation in knee osteoarthritis. Med Sci Sports Exerc 43(8):1538-1543, 2011. doi: 10.1249/MSS.0b013e3182118592.

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