β-Hydroxy β-Methylbutyrate
Leucine metabolite that helps prevent muscle breakdown and supports recovery, especially during caloric restriction or intense training.
HMB is a metabolite of the amino acid leucine. Its primary benefit is reducing muscle protein breakdown rather than increasing protein synthesis. Most effective for preventing muscle loss during caloric deficits, in older adults, or during very intense training periods. Benefits are more modest in well-trained individuals eating adequate protein.
Slows muscle protein breakdown
Supports muscle cell membrane integrity
How HMB works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
3g daily
Take with food
| Form | Type |
|---|---|
| 💊HMB-Ca (calcium salt) capsules or powder | Recommended |
| 💊HMB-FA (free acid) — faster absorption | Alternative |
HMB-FA absorbs faster and may be better pre-workout. HMB-Ca is more affordable and works well for daily use.
Minimum: 2 weeks
Optimal: 4 weeks
Cycling: Not required
Note: HMB-FA (free acid form) can be taken pre-workout for acute effects. HMB-Ca (calcium salt) is more common and can be taken anytime.
Preserves muscle during dieting or overtraining
Less soreness and faster strength recovery
Insufficient data; avoid supplementation
May be particularly beneficial for preserving muscle mass
Generally safe to combine with other supplements and medications
Tip: Take with food
Top studies from 38+ peer-reviewed papers
Moore ZE et al. • The Cochrane database of systematic reviews (2020)
“Evidence for the impact of nutritional interventions on the healing of foot ulcers in people with diabetes compared with no nutritional supplementation, or compared with a different dose of nutritional supplementation, remains uncertain, with eight studies showing no clear benefit or harm.”
Bear DE et al. • The American journal of clinical nutrition (2019)
“HMB, and supplements containing HMB, increased muscle mass and strength in a variety of clinical conditions, although the effect size was small.”
Comishen KJ et al. • Journal of thrombosis and haemostasis : JTH (2025)
“Many diagnoses were associated with bleeding disorders and, therefore, warrant investigation when assessing a patient with HMB of unknown etiology.”
Harlow J et al. • Nutrients (2024)
“Nutrition supplementation may have small benefits on muscle performance and recovery in warfighters.”
Vitale SG et al. • Medicina (Kaunas, Lithuania) (2022)
“However, such findings need to be confirmed by additional trials due to the high number of outdated studies and recent improvements in hysteroscopic instrumentation and techniques.”
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