HMB, or beta-hydroxy beta-methylbutyrate, is a supplement used by athletes and bodybuilders to promote muscle growth and reduce muscle damage. HMB is a metabolite of the amino acid leucine, and the body naturally produces small amounts of HMB. However, supplementing with HMB can increase HMB levels in the body and provide additional benefits. When choosing the best HMB supplement, there are a few key factors to consider. One of the most important factors is the purity and potency of the HMB. Look for a supplement that uses high-quality, clinically tested, and research-proven HMB. Also, pay attention to dosage and serving size, as these can vary greatly between products.