Supplementation with creatine typically results in weight gain, partly due to an increase in total body water.[1] The range of weight gain after a creatine loading phase tends to fall between 0.9 and 1.8 kg (1.98–3.96 lbs).[2][3] This may be of particular concern to individuals competing in weight-sensitive sports.
Diarrhea can occur when too much creatine is taken at one time,[4] in which case the doses should be spread out throughout the day and taken with meals.
Supplementation with creatine has been reported to negatively affect aerobic capacity to a small degree.[5] It has been speculated that this potential detrimental effect may be related to increases in total body water and body weight following supplementation with creatine.[6]