HMB
Also known as: β-hydroxy-β-methylbutyrate, HMB, Calcium HMB, myHMB
Downstream leucine metabolite (~5% of leucine→HMB conversion) that inhibits ubiquitin-proteasome pathway, supports membrane integrity via HMG-CoA reductase, and may activate mTOR.
Last reviewed: 2026-06-23 · 1 indexed study
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Overview
Beta-hydroxy-beta-methylbutyrate (HMB) is a leucine metabolite that reduces muscle protein breakdown and supports lean mass preservation, particularly in untrained, older, or catabolic states.
Mechanism & Function
Mechanism of Action
Reduces muscle protein degradation, supports membrane cholesterol synthesis, and may activate mTOR; effects strongest in catabolic or untrained populations.
Physiological Role
Strongest evidence in untrained, sarcopenic, or bedrest populations; modest effects in trained athletes; useful during cutting phases.
Primary Pathways
Performance / Health Relevance
Robust evidence in older adults, untrained, and catabolic states; trained-athlete data more mixed.
Evidence Review
Compare Calcium Forms
Full comparison7 calcium forms are indexed. Bioavailability, clinical evidence, and best-use cases differ meaningfully between them.
| Form | Evidence |
|---|---|
HMBThis page Ca-HMB ~80%; HMB-FA produces 2× higher peak plasma at same dose. | 68/100 |
| Calcium Caseinate DIAAS ≈ 1.18; complete EAA profile. | 78/100 |
| Calcium Citrate ~22–27% absorption regardless of stomach acidity. | 75/100 |
| Calcium Carbonate Calcium carbonate provides elemental calcium but requires gastric acid for absorption; absorption may be reduced on a completely achlorhydric stomach. | 67/100 |
| Vitamin B5 (Pantothenic Acid) Well-absorbed from the gastrointestinal tract. Bioavailability is generally high. | 65/100 |
| Calcium AKG Moderate. | 48/100 |
| Calcium Lactate One trial measured absorption from a calcium lactate drink; small differences in fractional absorption were observed when additional caseinophosphopeptide preparations were included, but these differences were judged unlikely to be biologically meaningful. | 45/100 |
Practical Use & Dosage
- Minimum Effective Dose
- 1.5 g/day
- Optimal Range
- 3 g/day in divided doses
- Upper / Caution Level
- ~6 g/day
- Timing
- With meals; pre/post-workout
- Best Format
- Capsule, powder (Ca-HMB or HMB-FA)
- Bioavailability
- Ca-HMB ~80%; HMB-FA produces 2× higher peak plasma at same dose.
- Absorption Considerations
- Rapid intestinal absorption; HMB-FA has improved PK over Ca-HMB.
Safety & Interactions
Side Effects
- •Generally well tolerated
Contraindications
- None established
Drug Interactions
- •None significant
Who Should Avoid
- •Pregnancy (limited data)
Monitoring
None routine.
Frequently Asked Questions
Auto-generated from indexed evidence — dosage, safety, interactions, and more.
When is HMB typically used or indicated?
HMB is most commonly used for: Anti-catabolic, Muscle preservation, Recovery, Sarcopenia prevention. Strongest evidence in untrained, sarcopenic, or bedrest populations; modest effects in trained athletes; useful during cutting phases.
How does HMB work?
Reduces muscle protein degradation, supports membrane cholesterol synthesis, and may activate mTOR; effects strongest in catabolic or untrained populations.
What is the recommended dose of HMB?
The optimal range is 3 g/day in divided doses. with a minimum effective dose of 1.5 g/day. Best taken: With meals; pre/post-workout. Upper / caution level: ~6 g/day.
What are the side effects of HMB?
Reported side effects include: Generally well tolerated. Monitoring: None routine.
Does HMB interact with medications?
Known or theoretical interactions: None significant. Always check with a clinician before combining with prescription medication.
Who should avoid HMB?
HMB is generally not recommended for: Pregnancy (limited data); and None established.
How strong is the evidence for HMB?
Evidence level: Moderate (overall score 68/100), based on 1 indexed study on SuppIndex.
Research & References (1)
HMB on muscle mass and strength: meta-analysis
Significant lean mass and strength gains, especially in older and untrained populations.
Trademark Ingredients
Related Ingredients
Other top-rated ingredients in Amino Acids.
L-Leucine
82/100Essential BCAA that activates mTORC1 via Sestrin2 sensing, driving phosphorylation of S6K1 and 4E-BP1, initiating cap-dependent translation and muscle protein synthesis.
Beta-Alanine
78/100A rate-limiting precursor to carnosine (β-alanyl-L-histidine) synthesis, enhancing intramuscular pH buffering capacity during high-intensity anaerobic exercise.
EAA Blend
78/100Free-form blend of 9 EAAs (Leu, Ile, Val, Lys, Met, Phe, Thr, Trp, His) at evidence-based ratios; bypasses gastric digestion for rapid plasma aminoacidaemia.
Research Overview
Moderate EvidenceCite this ingredient
One-click citation export in APA, MLA, Chicago, BibTeX, or HTML. The URL below is stable and safe to link.
Stable URL
https://thesuppindex.com/ingredients/hmb
SuppIndex. (2026). HMB: Evidence summary, dosage and clinical studies. Retrieved October 16, 2026, from https://thesuppindex.com/ingredients/hmb
Based on 1 indexed studies · Evidence level: Moderate.
Goal Ratings
Stack Compatibility
Pair with creatine, vitamin D, leucine; useful during caloric deficit.