[bhelkey]

What I got from the linked review is:

1) Creatine is safe, "creatine supplementation is safe across a range of doses, durations, and populations according to human trials".

2) Stomach issues are a commonly reported side effect, "Gastrointestinal issues were the most frequently reported side effect... Most notably, gastrointestinal distress is a commonly reported side effect, and those supplementing with creatine may need to divide the dose into smaller boluses to alleviate it; however, it is worth noting that this side effect was not persistent"

3) It is not clear if the side effects are caused by creatine, many of the issues can be explained by baseline issues rather than caused by creatine, "No consistent or clinically meaningful dose-dependent increases in side-effect reporting were observed across models; even at higher doses and prolonged durations, reporting remained low and largely comparable to placebo at the study level"