Creatine loading is generally considered safe for most people, experts say. “I’m not aware of any evidence that this approach has any harmful effects,” Dr. Schoenfeld explains.
Creatine loading may cause mild side effects such as gastrointestinal discomfort, diarrhea, or fluid retention in some people, especially during the first few days of the loading process.
“When you take creatine, your creatine levels increase, which can lead to fluid retention. Although you may see weight gain on the scale, this is actually just a temporary increase in total body water,” explains Los Angeles-based sports nutritionist Jessica Isaacs. It’s believed that short-term fluid retention during creatine supplementation occurs due to changes in water pressure inside and outside cells, which allows water to enter cells.
To reduce the chance of side effects, experts recommend starting with small amounts of no more than 10 grams throughout the day.
“There’s a common misconception that creatine supplements are bad for kidney health because they’ve been shown to affect a common measure of kidney function called creatinine. However, when used as recommended, creatine supplements don’t appear to cause kidney damage or dysfunction in healthy people,” explains Isaacs.
In fact, “one study found that a 12-week creatine supplementation protocol showed no significant differences in kidney function between an experimental group taking creatine and a control group taking a placebo,” Isaacs added.
Isaacs also pointed to a 2020 systematic review of the scientific literature on creatine supplementation in women, which found no adverse effects related to kidney function in experimental and control groups.
Creatine supplementation is considered safe and effective for most healthy adults, but additional research may be needed to evaluate its safety in children and adolescents.
