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Leucine-metabolite supplement · Fact sheet

HMB

Also known as Beta-hydroxy-beta-methylbutyrate · Calcium HMB

HMB is a leucine metabolite studied for muscle preservation and training outcomes. Small trials suggest context-dependent benefits, especially during muscle-loss risk, but gains in lean mass do not always translate into better function.

Not FDA approvedEarly human evidence
Muscle & recovery

What is HMB?

Calcium HMB and free-acid HMB are different formulations and should not be assumed identical.

Older-adult bed rest, sarcopenia and trained-athlete performance are different use cases.

Benefits & claims

Interest in HMB spans recovery. Study findings apply to the named formulation and population.

What the evidence supports

  • The bed-rest trial analyzed 19 participants and its favorable lean-mass analysis excluded one subject.
  • The sarcopenia trial reported improved strength and performance with concurrent training.
  • Small condition-specific findings do not establish unusually large bodybuilding gains.
Research areas
  • Formulation-specific human outcomes
  • Mechanistic research

Dosage & frequency

Human study context

This is an exposure from a named human study, not a generally established treatment or enhancement regimen.

Older-adult bed-rest HMB study

24 healthy older adults randomized; 19 evaluable after bed rest

Amount
1.5 g HMB as calcium salt per administration; 3 g/day total
Frequency
Twice daily, starting five days before ten days of bed rest and continuing through eight weeks of rehabilitation
Route studied or labeled
Oral

The study assessed muscle-loss protection in a controlled setting, not an athletic enhancement program. Functional differences were not detected, and the favorable lean-mass analysis had an exclusion.

Effect of β-hydroxy-β-methylbutyrate (HMB) on lean body mass during 10 days of bed rest in older adults.
How to read these amounts

An approved regimen belongs to a specific product, indication, and population. A study regimen describes what researchers tested; it does not establish a prescription or a safe self-use protocol. Products, routes, and formulations are not interchangeable. A prescriber uses the full label and individual clinical circumstances.

Personal accounts may describe amounts, schedules and outcomes beyond clinical research. They do not establish a regimen. Read the reported experiences

Formulations, interactions & practical context

Formulation differences

  • Older-adult bed rest, sarcopenia and trained-athlete performance are different use cases.

Interactions & precautions

  • The reviewed sources do not establish a comprehensive human interaction profile for this exact substance or combination.

What is still unresolved

  • Reproducibility in larger independent trials
  • Long-term outcomes and adverse effects
  • Equivalence of different preparations and interaction profiles
Effect of β-hydroxy-β-methylbutyrate (HMB) on lean body mass during 10 days of bed rest in older adults. Effects of Beta-Hydroxy-Beta-Methylbutyrate Supplementation on Older Adults with Sarcopenia: A Randomized, Double-Blind, Placebo-Controlled Study. NIH ODS: exercise and athletic-performance supplements

Side effects & risks

  • Short studies cannot establish long-term safety or interactions in every frail or medically complex population.
  • Multi-ingredient nutrition studies cannot isolate the effect of HMB alone.

This is a summary of the cited evidence, not a complete product label. A lack of human safety data does not establish safety.

Clinical research

Early human evidence

A small older-adult bed-rest study found less lean-mass loss but no detectable functional difference. Another small sarcopenia trial studied HMB alongside resistance exercise.

Studies

Personal experiences

Reports describe what someone noticed. They cannot establish cause, typical results, or how often a side effect happens. Amounts and schedules describe the individual account, not an effective or safe dose. Product identity and strength may be unverified, and missing details are left explicit.

No attributable personal accounts were found in the sources reviewed.

Approval status

No FDA-approved HMB drug indication is established for the supplement uses discussed here. Supplement availability is not FDA approval of efficacy or safety.

No FDA-approved product for this entry

Approval covers the labeled product, use and population. A trial phase does not establish success; a stopped program is not ongoing research.

Open questions

  • Reproducibility in larger independent trials
  • Long-term outcomes and adverse effects
  • Equivalence of different preparations and interaction profiles

Summary

Small condition-specific findings do not establish unusually large bodybuilding gains.

Sources

Medical evidence and regulatory sources are listed here. Personal reports are linked separately in the experiences section.

  1. pubmedEffect of β-hydroxy-β-methylbutyrate (HMB) on lean body mass during 10 days of bed rest in older adults.

    24 randomized older adults; 19 evaluable after bed rest, with analysis limitations.

  3. nihNIH ODS: exercise and athletic-performance supplements

    Ingredient-specific efficacy, tolerability and evidence limits for performance supplements.

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