HMB
Beta-Hydroxy Beta-Methylbutyrate
HMB (β-Hydroxy-β-Methylbutyrate) is a metabolite of the branched-chain amino acid leucine. Approximately 5% of dietary leucine is converted to HMB in the body. Used in clinical and sports contexts to reduce muscle protein breakdown, support recovery, and prevent muscle loss in catabolic states (bedrest, illness, severe caloric restriction).
Divided doses or pre-workout.
Start here. Every protocol below is ordered lowest-first. Begin at the smallest effective dose, hold about a week to assess tolerance, and step up only if needed.
How it works
HMB acts through multiple anti-catabolic mechanisms:
Reduced Muscle Protein Breakdown
HMB decreases ubiquitin-proteasome activity, reducing muscle protein degradation. This is the primary mechanism.
Improved Cell Membrane Integrity
HMB is a precursor for cholesterol synthesis - supports muscle cell membrane stability under stress.
Reduced Muscle Damage
Lower CK and LDH elevation post-exercise indicate reduced muscle damage.
Modest Anabolic Signaling
Some mTOR pathway activation, but effect is smaller than leucine alone.
Particularly Useful in Catabolic States
Effect sizes larger when baseline catabolism is high (caloric deficit, bedrest, illness, sarcopenia).
What to expect
Days 1-14: subtle effects.
Weeks 4-12: peak effects in catabolic contexts.
Long-term: sustained anti-catabolic with continued use.
Evidence
Claims we could not support
No abstract we checked supports these for this molecule at this route. That is not the same as saying they are false — it marks where the evidence is missing.
Dose/route: 1-3g daily; Oral capsule or powder; 1-3x daily. No checked live PubMed abstract verified this exact displayed dose, route, and frequency for the same molecule/formulation and relevant population.
Mechanism: HMB acts through multiple anti-catabolic mechanisms: 1. Reduced Muscle Protein Breakdown: HMB decreases ubiquitin-proteasome activity, reducing muscle protein degradation. This is the primary mechanism. 2. Improved Cell Membrane Integrity: HMB is a precursor for cholesterol synthesis - supports muscle cell membrane stability under stress. 3. Reduced Muscle Damage: Lower CK and LDH elevation post-exercise indicate reduced muscle damage. 4. Modest Anabolic Signaling: Some mTOR pathway activation, but effect is smaller than leucine alone. 5. Particularly Useful in Catabolic States: Effect sizes larger when baseline catabolism is high (caloric deficit, bedrest, illness, sarcopenia).. No checked live PubMed abstract provided an exact-molecule/formulation sentence supporting this source-JSON mechanism claim.
Primary safety claim: No primary safety text present in source JSON. No checked live PubMed abstract directly verified this source-JSON safety claim at the displayed formulation, route, and regimen.
Side effects & safety
Commonly reported
- Generally well-tolerated
- Mild GI possible
Less common & notes
- Allergic reactions rare.
- Long-term safety good.
Pharmacokinetics
Plasma
(free-acid) or 1-2 hours (calcium)
Hours plasma; cumulative tissue effects over weeks
Oral ~50-80% (free-acid > calcium)
Daily dosing for sustained anti-catabolic effects
Hepatic and tissue
Storage. Capsule/powder. Cool dry location.
Regulatory status
Dietary supplement (US, DSHEA). Used in some clinical nutrition products.
Put it to work
Calculate, log & track
Open HMB straight into OnePin with your vial and dose pre-filled, then let it handle the syringe math and remind you before the vial runs out.
Open HMB in the app →Go deeper
The guide & community
The complete HMB walkthrough, real protocol discussion and coaching live inside the BlessUp community on Skool.
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