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The Supplement Research Compendium
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HMB

β-Hydroxy β-Methylbutyrate

Leucine metabolite — preserves muscle in aging, not in young lifters.

Mixed evidence ⚡Performance

✚ Updated · How we grade evidence

Evidence tier
Mixed
Research weight
Citations
8 verified / 8
Classification
Performance
❝
What the evidence says. Graded mixed: meta-analyses in adults over 50 show small but real gains in lean mass and grip/function, yet in young trained subjects pooled trials find no effect on body composition or strength — so the benefit is population-dependent and modest, not the broad muscle-builder it's marketed as. (Mixed evidence: Conflicting results across studies; benefit uncertain.)

What is HMB?

HMB (β-Hydroxy β-Methylbutyrate) is a performance supplement used for preserve muscle in aging. NutriDex grades the human evidence as Mixed. HMB is a metabolite of the amino acid leucine, sold to build muscle and speed recovery. The evidence splits sharply by population. In adults over 50, several meta-analyses find modest but consistent benefits: fat-free mass rises by roughly 0.3–0.4 standardized units (about 0.3 kg of lean mass, up to ~1.5 kg appendicular muscle in the largest 2025 pooling), with small improvements in grip strength and chair-stand time, typically needing 3 g/day for 12+ weeks. In young, resistance-trained adults the picture is different — a 2020 meta-analysis of 11 RCTs found no significant effect on body composition or strength. Benefits appear concentrated in anti-catabolic settings (aging, sarcopenia, bed rest, clinical wasting) rather than muscle-building in healthy athletes. Effect sizes are small and several trials are industry-linked, so expectations should stay measured.

Purported Benefits

✓Preserve muscle in aging
✓Slow muscle wasting
✓Modest lean-mass gains (older adults)
✓Reduce muscle-damage markers

Evidence by outcome

The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.

OutcomeEvidenceEffectStudies
Preserve/increase lean mass in older adultsMultiple meta-analyses in adults >50 show small consistent fat-free-mass gains (SMD ~0.35); needs 3 g/day ≥12 wk. Moderate ↑ benefit · small 3
Build muscle/strength in young trained adults11-RCT meta-analysis in young subjects found no significant effect on fat-free mass or strength during resistance training. Moderate — no effect · negligible 1
Improve strength/physical function (older/sarcopenic)One large pooling found small grip/chair-stand gains; another found no added benefit when HMB is added to exercise. Mixed ↔ mixed · small 2
Added benefit over exercise aloneMeta-analysis: adding HMB to exercise gave no significant extra muscle/strength gain in sarcopenic patients. Moderate — no effect · negligible 1

Dosing & Compounds

Typical Dose
3 g/day, usually split into 1 g doses with meals; HMB-Ca and free-acid forms perform similarly, with effects most likely after 12+ weeks.
Active Compounds
Calcium β-hydroxy-β-methylbutyrate (HMB-Ca)Free-acid HMB (HMB-FA)

Safety & Cautions

HMB is well tolerated: human trials and reviews report no serious adverse effects at up to 3 g/day, and no negative impact on blood glucose, insulin sensitivity, lipids, or liver and kidney markers. Mild GI complaints (nausea, heartburn, flatulence) are the main reported issues. There are no well-established drug interactions, but data in pregnancy, breastfeeding, and children are lacking, so it is not recommended for them; anyone with kidney or liver disease should consult a clinician before use. Educational only — always check with your doctor or pharmacist before combining HMB with any medicine.

Key Studies

Meta-analysis Frontiers (over-50) 2025 ✓ Full text
21 RCTs, 1935 adults >50: HMB raised appendicular muscle ~1.56 kg and lean mass 0.28 kg; grip +0.54 kg; chair-stand −0.73 s. Best at 3 g/day >12 wk.
Systematic review Su 2024 ✓ PubMed
Systematic review/meta-analysis in sarcopenia: HMB or HMB-rich supplements modestly improved muscle-mass measures but overall evidence quality was low.
Meta-analysis Chen (exercise±HMB) 2024 ✓ PubMed
Adding HMB to exercise gave no significant extra gain in muscle mass, strength or physical performance vs exercise alone in sarcopenic patients.
Systematic review Bideshki 2025 ✓ Full text
Umbrella review of meta-analyses: HMB benefits on body composition/strength are small and most pronounced in older or clinical populations, not young athletes.
Meta-analysis Jakubowski 2020 ✓ PubMed
Meta-analysis of 11 RCTs in young subjects: no significant HMB effect on fat-free mass (+0.29 kg, p=0.06) or strength during resistance training.
Meta-analysis Lin 2021 ✓ PubMed
9 studies, 448 older adults: HMB significantly increased fat-free mass (effect size 0.37, 95% CI 0.16–0.58); little added benefit when combined with exercise.
Meta-analysis Wu 2015 ✓ PubMed
7 RCTs, 287 older adults: HMB preserved muscle mass (SMD 0.35 kg, 95% CI 0.11–0.59) with no change in fat mass.
Review ISSN Position Stand 2024 ✓ PubMed
Reviews tolerability: HMB up to 3 g/day is well tolerated with no adverse effects on glucose, insulin, lipids, liver or kidney markers in humans.
8 sources cited · 8 verified Search all studies on PubMed ↗

Common questions about HMB

What is HMB used for?

HMB is most often taken for Preserve muscle in aging, Slow muscle wasting, Modest lean-mass gains (older adults), Reduce muscle-damage markers. Leucine metabolite — preserves muscle in aging, not in young lifters.

Does HMB work — what does the evidence say?

Mixed evidence. Conflicting results across studies; benefit uncertain. HMB is a metabolite of the amino acid leucine, sold to build muscle and speed recovery. The evidence splits sharply by population. In adults over 50, several meta-analyses find modest but consistent benefits: fat-free mass rises by roughly 0.3–0.4 standardized units (about 0.3 kg of lean mass, up to ~1.5 kg appendicular muscle in the largest 2025 pooling), with small improvements in grip strength and chair-stand time, typically needing 3 g/day for 12+ weeks. In young, resistance-trained adults the picture is different — a 2020 meta-analysis of 11 RCTs found no significant effect on body composition or strength. Benefits appear concentrated in anti-catabolic settings (aging, sarcopenia, bed rest, clinical wasting) rather than muscle-building in healthy athletes. Effect sizes are small and several trials are industry-linked, so expectations should stay measured.

What is the typical dose of HMB?

3 g/day, usually split into 1 g doses with meals; HMB-Ca and free-acid forms perform similarly, with effects most likely after 12+ weeks.

Is HMB safe? Any cautions or side effects?

HMB is well tolerated: human trials and reviews report no serious adverse effects at up to 3 g/day, and no negative impact on blood glucose, insulin sensitivity, lipids, or liver and kidney markers. Mild GI complaints (nausea, heartburn, flatulence) are the main reported issues. There are no well-established drug interactions, but data in pregnancy, breastfeeding, and children are lacking, so it is not recommended for them; anyone with kidney or liver disease should consult a clinician before use.

How many studies support HMB?

NutriDex cites 8 sources for HMB, graded "Mixed".

Cite this page
APA

Peh, D. (2026). HMB (β-Hydroxy β-Methylbutyrate): Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 26 Jun 2026, from https://nutridex.info/s/hmb

BibTeX
@misc{nutridex_hmb,
  author       = {Peh, Daryl},
  title        = {HMB (β-Hydroxy β-Methylbutyrate): Benefits, Dosage, Side Effects \& Evidence},
  year         = {2026},
  howpublished = {NutriDex --- The Supplement Research Compendium},
  url          = {https://nutridex.info/s/hmb},
  note         = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-06-26}
}

For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.

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