Creatine is an “osmotically active substance,” it pulls water into your muscle cells, which increases protein synthesis.
A common knock against creatine is that it’s bad for the liver, but this doesn’t withstand scrutiny.
A number of human studies have looked specifically at creatine usage and liver parameters and found no association between the supplement and liver problems.
Elevated creatinine levels in and of themselves aren’t a problem. They can be indicative of kidney problems, but they can also occur independent of kidney problems. On some level, it’s understandable that this caused someone to sound the alarm, but it doesn’t make it a reason to avoid taking creatine.
Rat studies on a model with two-thirds nephrectomy—literally removing 66 percent of the kidney—found no issues with creatine. There is also a case study of a man with a single kidney having no problems with 20 grams of creatine daily alongside his high-protein diet.
Creatine does not cause damage to skeletal muscle or the heart, liver, or kidneys.
Creatine, at this moment in time, seems to be fine for kidney disorders that are not characterized by edema and tissue swelling.
Based on limited research, it is probably wise to avoid creatine supplementation if you have polycystic kidney disease, focal segmental glomerulosclerosis, or another kidney disorder characterized by tissue swelling.