HMB
- Effective dose
- 3–3 g
- Evidence
- 3/5· Moderate
Last updated June 1, 2026
What it is
HMB (beta-hydroxy-beta-methylbutyrate) is a metabolite of the amino acid leucine. It is thought to reduce muscle protein breakdown and support repair, which is why it is studied mainly for recovery and preservation of lean mass.
Benefits
May attenuate exercise-induced muscle damage and support strength and lean mass, with the clearest effects in untrained individuals and during intense or novel training. The ISSN cites about 38 mg per kg body weight daily (roughly 3 g/day), used for at least two weeks.
When to take it
Take close to the workout: the calcium form about 60-120 minutes before, the free-acid form about 30-60 minutes before. Most effective when used for at least two weeks before intense training.
Side effects
Considered safe in young and older adults at doses up to about 6 g/day, with no consistent adverse effects on liver, kidney, or blood markers reported.
Sources
Products containing HMB
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