HMB is a supplement made from a protein building block, used mainly to help preserve muscle. Evidence most consistently supports protecting muscle in older adults and during illness or forced rest, and easing soreness after hard exercise. Benefits for building muscle in trained young people are small. Safety is strong short-term; long-term use is untested. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Lean body mass (DXA) | Stable or increasing for age | Primary target: tracks muscle preservation |
| Grip strength | ≥ ~40 kg (men), ≥ ~27 kg (women) | Proxy for whole-body strength and mortality risk |
| Gait speed | > 1.0 m/s | Functional marker of mobility and independence |
| Fasting glucose | 70–90 mg/dL | Screens the uncertain metabolic effect of HMB |
| Hemoglobin A1c | < 5.4% | Longer-term blood-sugar control |
| Lipid panel (total, LDL, triglycerides) | LDL < 100 mg/dL; triglycerides < 90 mg/dL | Captures HMB's small cholesterol effect and cardiometabolic health |
| eGFR | > 90 mL/min/1.73m² | Confirms kidney function, HMB's main clearance route |
| ALT / AST | ALT < 25 U/L (men), < 22 U/L (women) | Confirms liver health where HMB is processed |
Cadence: Baseline, then reassess function and body composition at ~3 months and every 6–12 months; check metabolic and organ-safety labs annually (or sooner with kidney, liver, or blood-sugar concerns).