HMB

Beta-Hydroxy Beta-Methylbutyrate · Calcium HMB

Snapshot

Indications	Contraindications
Sarcopenia^1–7 Muscle strength in older adults^1–7 Exercise-induced muscle damage⁸ Cancer-related muscle loss⁹ Nutrition after hip fracture¹⁰ Cardiac surgery recovery¹¹ Endurance performance^12–14	Pregnancy or breastfeeding¹⁵ Under age 18¹⁵

Beta-hydroxy-beta-methylbutyrate (HMB) is a breakdown product of the amino acid leucine¹⁶. It acts by suppressing muscle protein breakdown and supporting protein synthesis⁸. Supplementation is used to preserve muscle mass and strength in older adults and in sarcopenia^{1, 2}, to limit exercise-induced muscle damage⁸, and for muscle loss in cancer, where trials are mixed. Typical patients are older adults with sarcopenia and people with illness-related muscle wasting¹⁷.

Meta-analyses find small gains in muscle mass and strength^{4, 17}. In sarcopenia the benefit is confined to strength measures such as handgrip, with little effect on gait speed^{2, 3}. In cancer, two small studies showed benefit and a larger study did not¹⁶. In a 2024 cross-sectional study of community-dwelling older adults, lower endogenous plasma HMB was associated with frailty, and the authors called for targeted supplementation trials¹⁸. Products supply HMB as a calcium salt or free acid¹⁶, with 442 products listing HMB; see Form comparison.

Memorial Sloan Kettering notes that it is unknown whether HMB blunts mammalian target of rapamycin (mTOR) inhibitors used in cancer treatment¹⁶. Health Canada labels ask for a practitioner's advice before use with cholesterol-lowering medication¹⁹.

Last updated October 16, 2026. Read how we make monographs.

In the full monograph

70 sources, 55 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources