HMB, or Hydroxymethylbutyrate, is a byproduct of leucine, which is an amino acid, and it is used for making medicine. It may be effective for increasing muscle and body weight in people with AIDS, according to RxList.
The effectiveness of HMB has also been rated for treating cardiovascular disease, lowering blood pressure and high cholesterol, and building muscle, but the evidence is insufficient. HMB works to promote muscle growth by reducing destructive muscular breakdown. It appears safe for most people to take for a short time. Up to 8 weeks is considered safe with a recommended dosage of 3 to 8 grams per day, according to RxList. Pregnant or breastfeeding women should not take HMB.