HMB is a leucine breakdown product taken to help preserve and build muscle. Its most believable benefits appear where muscle is actively being lost — bed rest, illness, low food intake, and age-related muscle loss — with small gains in muscle and grip strength. It offers little for healthy, well-trained people. Safety is reassuring. (Full Review)

Protocol

Standard Dose

3 g / day

~38 mg/kg body weight per day; most-studied regimen.

Split Dosing

2–3 doses

Plasma HMB clears within hours; split with meals, anchored around exercise.

Form Selection

HMB-Ca or HMB-FA

Free acid raises blood levels faster and higher; outcome differences not firmly established.

Time to effect

Clinical / Aging

Weeks to months

Effects accrue alongside training and adequate protein.

Trained Individuals

≥ 6 weeks

Strength and body-composition effects emerge only after consistent use.

Loading Phase

None required

Unlike creatine, HMB does not require a loading phase.

Benefits

Medium: Preservation of muscle mass during catabolic states; muscle mass and strength in sarcopenia and older adults; faster recovery and reduced muscle damage after intense exercise.

Low: Strength and power gains in untrained individuals; support of body composition with resistance training; aerobic performance in trained athletes.

Speculative: Countering disuse atrophy and aiding rehabilitation; metabolic and glucose effects in younger adults.

Contraindications

Pregnant and breastfeeding women

Children and adolescents

Significant liver or kidney impairment (medical supervision only)

Key Interactions

Prescription drugs (caution, theoretical)

Risk & Side Effects

Low: Mild gastrointestinal discomfort.

Speculative: Theoretical effects from long-term use beyond one year; unstudied effects in pregnancy, lactation, and adolescents; reliance on manufacturer-linked safety data.

Monitoring

Marker	Target	Why
Lean body mass (DXA or BIA)	Stable or increasing for age and sex	Tracks the muscle-preservation goal directly
Handgrip strength	At or above age- and sex-referenced norms	Validated proxy for whole-body strength and sarcopenia
Gait speed (4-meter walk)	≥ 1.0 m/s	Functional performance marker; predicts mobility and outcomes
SPPB	≥ 10 of 12	Composite of balance, gait, and sit-to-stand for functional status

Cadence: Baseline, reassess at ~8–12 weeks, then every 3–6 months.

Qualitative Assessment

Subjective strength and ease with daily tasks (e.g., carrying, rising from a chair)
Recovery quality and muscle soreness after training
Energy and overall sense of physical capability
Maintenance of muscle and function during a period of reduced activity or illness

HMB for Health & Longevity

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment