People often confuse creatine (a supplement) with creatinine (a blood marker). Creatine supports phosphocreatine stores in muscle and may cause mild water retention and a small scale-weight increase that is not body fat. Higher doses can trigger gastrointestinal upset (bloating/diarrhea) and cramps in some users. In people with known kidney disease—or those using medications that can stress the kidneys—professional guidance is recommended before supplementation. If the concern is actually elevated creatinine, the causes may include dehydration, intense exercise, high meat intake, certain drugs, or reduced kidney filtration. Clinically, decisions are not based on a single number: eGFR trends, urine albumin/protein, blood pressure, and symptoms are interpreted together.