Specialty Supplement 4x The HMB♦ Provides Muscle & Strength Support Calcium B-Hydroxy - B-Methylbutyrate Monohydrate Dietary Supplement Specialty Supplement MET-Rx® HMB 1000 HMB is a metabolite of leucine, a Branched Chain Amino Acid. May help support strength levels and muscles when used in combination with weight training. ♦Per capsule, compared to our previous HMB 250 mg Formula.