Creatine supplementation in patients with kidney disease - harm or benefit?

Creatine is one of the most widely used nutritional supplements and has a well-established role in cellular energy metabolism, skeletal muscle performance, and exercise capacity. More recently, growing evidence suggests that its biological effects extend beyond ergogenic benefits to include the preservation of muscle mass and strength, neuroprotection, modulation of inflammation and oxidative stress, and maintenance of cellular homeostasis. These properties are particularly relevant in clinical conditions characterized by sarcopenia, frailty, and neurocognitive impairment, including chronic kidney disease (CKD) and aging. At the same time, concerns persist about the renal safety of creatine supplementation, especially in individuals with impaired kidney function. Emerging data also indicate that creatine may influence gut physiology by modulating intestinal barrier integrity, immune responses, and inflammatory pathways. Given the widespread and growing use of creatine among athletes, older adults, and patients with chronic diseases, a comprehensive evaluation of its pleiotropic effects is timely. This narrative review aims to critically examine the current evidence regarding the renal safety of creatine supplementation, its effects in patients with CKD, and its potential benefits for sarcopenia, cognitive function, and the gut microbiota. Mechanistic, experimental, and clinical evidence is integrated to provide a comprehensive overview of creatine as a promising nutritional strategy for CKD management.