HMB (Beta-Hydroxy Beta-Methylbutyrate)
Also known as: β-Hydroxy β-Methylbutyrate, Calcium HMB, HMB-Ca, β-hydroxy-β-methylbutyric acid
Effective Dosage
1.5–3 g daily based on study doses
What the Science Says
HMB is a natural byproduct of the amino acid leucine, produced in small amounts when your body breaks down protein. It is most commonly marketed to older adults to help slow muscle loss (sarcopenia), and some small trials suggest it may modestly improve physical performance markers like chair-stand speed or arm muscle circumference in elderly or sarcopenic patients. However, a 2026 meta-analysis of 13 randomized controlled trials found that HMB added to resistance training did not significantly improve fat mass, muscle mass, or muscle strength in adults over 50.
What It Doesn't Do
Does not reliably build muscle mass — the best available meta-analysis found no meaningful effect. Won't replace resistance training. Not proven to work in healthy, active adults. Adding it to your workout routine is unlikely to give you an edge. Early marketing claims about dramatic muscle gains are not supported by current evidence.
Evidence-Based Benefits
HMB is a metabolite of the amino acid leucine and has been shown to support muscle mass and strength, particularly in individuals undergoing resistance training or recovering from injury. It may also help reduce muscle protein breakdown, thus aiding in recovery and performance.
Strong EvidenceEffective at: 3-6 g daily
Source: auto-research
Absorption & Bioavailability
Unknown from provided studies — calcium HMB salt form is commonly used in trials, but absorption data were not reported in the provided papers.
Red Flags to Watch For
- A 2026 meta-analysis of 13 RCTs found no significant benefit for muscle mass, fat mass, or strength in older adults doing resistance training — directly contradicting common marketing claims.
- Most positive findings in provided studies are within-group improvements (not vs. placebo), which can be misleading and do not prove HMB caused the benefit.
- Several studies are small pilots (as few as 21 participants) with high risk of bias — results should not be generalized.
- HMB is often sold in combination products (with protein, creatine, prebiotics), making it impossible to isolate HMB's specific contribution.
- 442 registered supplement products contain HMB, suggesting heavy commercial interest that may outpace the actual evidence base.
Research Sources
- PubMed
- NIH DSLD
This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-04-06