在過去的十年裡，肌酸深受運動員與教練的歡迎。增補肌酸的注意力總是放在對於運動表現的影響，然而，卻鮮少有研究將焦點放在肌酸攝取後的副作用方面。短期與長期增補肌酸最為常見的副作用便是身體體重的增加，而這種現象與肌肉內水分含量的增加以及去脂體重的增加有關。肌肉內水分的保留可能與肌肉吸收肌酸時，所引起的滲透性腫脹有關。肌酸也可能作用在轉錄與轉譯層級，進而刺激收縮性蛋白的生物合成作用。另一個增補肌酸的副作用是在運動前立即與／或運動時攝取高劑量肌酸而引起運動時的腸胃道不適。除了這些副作用之外，在短期增補肌酸之後，對於健康運動員的腎臟與心臟功能、肌肉痙攣與拉傷，甚至是致癌性，並沒有明顯的負面影響。儘管如此，目前在人體上仍缺乏長期（＞1年）且控制嚴謹的安全性資料，也由於目前仍缺乏副作用的科學性證據，因此並無法保證這類產品的長期安全性。

In the last decade, the creatine monohydrate has been very popular among athletes and coaches. The attentions of creatine supplementation always were made on the effects of performance, however, there had few studies focused on the side-effects after ingestion of creatine. The most common side-effect of short- and long-term creatine supplementation is increased body weight, and this phenomenon is related to the increased intramuscular water content and fat-free mass. The intramuscular water retention may due to the osmotic swelling associated with muscle creatine uptake. Creatine may also function at the transcriptional or translational level to stimulate contractile protein biosynthesis. Another side-effect of creatine is gastro-intestinal distress during exercise while taking high doses of creatine immediately before and/or during exercise. Except these side-effects, there are no observable adverse effects on the kidney and heart functions, muscle cramps and strains, even the carcinogenicity, in health athletes after short-term creatine supplementation. However, the controlled long-term safety data (>1 year) in humans are lacking and thus the absence of scientific evidence for adverse side-effects to date does not prove product long-term safety.