HMB
Also sold as: Beta-hydroxy beta-methylbutyrate · Ca-HMB · HMB free acid
A leucine metabolite studied for preserving muscle during aging or catabolic illness and for training recovery. Results in already trained athletes are inconsistent.
Energy
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Research
- Energy: A single small RCT reported aerobic-capacity improvement, not greater strength; this does not establish relief of everyday fatigue.
REALITY CHECK // HMB is not a mild steroid. The largest trained-athlete gains cluster in commercially linked research and conflict with independent negligible-effect trials; free-acid kinetic advantages are also disputed by newer calcium-salt exposure data.
Levels: how we grade evidence. Grey = evidence of no benefit; amber = evidence it makes this goal worse.
Ratings are self-reported by a self-selected group of users: how it felt, not proof that it works.
Check your bottle
Compare what your label says with what was used in trials. This is a trial range, not a personal prescription.
Enter the amount from your label to see the result.
How it was studied
01 // STUDIED_DOSE_RANGE
Trial context
Most studies use about 3 g/day, often divided as 1 g three times daily, over weeks to months; some investigate up to 6 g/day with less safety evidence. Reports vary between calcium-salt mass and HMB-equivalent mass, so check the trial and label basis.
02 // TIMING_&_MATRIX
Form and schedule
Often split into three daily doses in studies. Faster pre-exercise kinetics have not established a superior chronic schedule.
03 // EVALUATION_WINDOW
Outcome-specific follow-up
Trials generally last weeks to months; the cited athlete study lasted 12 weeks. Body composition, strength and recovery require separate endpoints.
04 // SAFETY_&_QUALITY_GATE
Review before use
Pregnancy, breastfeeding and pediatric safety are insufficient. Kidney/liver disease, cancer and perioperative use require the treating team. Trials in cirrhosis do not establish unrestricted use in all liver or kidney disease.
UPPER LIMIT // No numerical EFSA/NIH UL is established. Common 3 g/day study use is not an official UL; chronic high-dose safety above the studied range is uncertain.
Summary
The most plausible clinical niche is preserving lean mass in older or catabolic patients. Large strength and hypertrophy claims in trained adults conflict with independent null trials, and improved biomarkers do not guarantee better performance.
Mechanism
HMB is a leucine metabolite investigated for muscle protein synthesis and reduced protein breakdown. Acute protein-metabolism effects do not establish chronic strength gains.
Typical studied dose
Most studies use about 3 g/day, often divided as 1 g three times daily, over weeks to months; some investigate up to 6 g/day with less safety evidence. Reports vary between calcium-salt mass and HMB-equivalent mass, so check the trial and label basis.
Upper limit
No numerical EFSA/NIH UL is established. Common 3 g/day study use is not an official UL; chronic high-dose safety above the studied range is uncertain.
Popular stacks with HMB
Not enough stack data yet. A combination with HMB appears here once 5 people rate the same set.
Forms and label traps
| Form on label | Active content | Studied range / day | Absorption & GI tolerance | Verdict |
|---|---|---|---|---|
| Calcium HMB monohydrate Best for: An established, widely used calcium-salt formulation. |
80% elemental / active | 2400–3000 mg | Older studies favor faster free-acid peaks; a 2024 study found greater calcium-salt total exposure (AUC). Generally well tolerated at commonly studied amounts. |
Studied standard [FORM // REFERENCE] Approximate composition: 1 g calcium salt contains 0.8 g HMB. The broad 2400-3000 mg HMB-equivalent interval reflects common 3 g salt versus 3 g HMB reporting; verify each paper, not a therapeutic target. |
| HMB free acid Best for: Comparing a specifically declared free-acid dose. |
100% elemental / active | 3000–3000 mg | Some early kinetic studies report faster peaks; faster peaks do not prove greater chronic efficacy, and newer AUC findings favor calcium salt. Usually tolerated in studies. |
Good option [FORM // GOOD] 100% denotes pure HMB free acid composition, not absorption. Include only declared HMB content, not the total gel or capsule mass. |
Common label traps
- TRAP_01 // Steroid-like muscle growth
Large commercially linked trial effects conflict with independent null findings. - TRAP_02 // Free acid is clinically superior
Conflicting pharmacokinetic studies do not establish superior strength or hypertrophy. - TRAP_03 // Works equally well in everyone
Older or catabolic populations cannot be substituted for healthy experienced lifters.
Other outcomes studied
Outside the five leaderboard goals. Same evidence levels as above.
- Older-adult lean mass Limited · benefit
Reviews show small-to-moderate but heterogeneous lean-mass benefits in older or sarcopenic adults; strength and function respond less consistently.
PMID 33034021 PMID 41305674 PMID 30697623 PMID 37248756 PMID 34081113 PMID 38171034 PMID 30360984 PMID 34179932 PMID 29300431 - Trained-adult hypertrophy Limited · benefit
A 12-week free-acid RCT reported large gains, while independent calcium-salt/free-acid trials found negligible strength and hypertrophy effects. Commercial affiliations are a material limitation.
PMID 24599749 PMID 30859862 PMID 29037326 - Recovery biomarkers Limited · benefit
Some trials lower CK, inflammatory markers or improve work-capacity recovery; another trial found no attenuation of damage. These acute markers do not prove chronic hypertrophy.
PMID 23286834 PMID 29420925 PMID 23908318 PMID 24639242 PMID 20072045 PMID 24500432 - Clinical muscle preservation Limited · benefit
A clinical meta-analysis favors muscle-mass preservation more than strength/function; many cancer, bed-rest and surgical trials are combination nutrition studies.
PMID 30982854 PMID 41102810 PMID 34371806 PMID 28705993 PMID 37099902 PMID 39765161 PMID 15080599 PMID 23919746 - Aerobic capacity Limited · benefit
One small RCT of trained and untrained males reports aerobic-capacity support without greater strength; replication is needed.
PMID 42441818 - Body fat Limited · benefit
An older commercially linked meta-analysis found small body-composition effects, including about 0.28% additional lean-mass gain per week; independent confirmation in trained adults is weak.
PMID 12433852 - Tolerability Moderate · benefit
Common study doses around 3 g/day are generally well tolerated; short-term safety cannot establish indefinite high-dose safety.
PMID 10917905 PMID 34371806
Reader questions
Is HMB worthwhile for an experienced lifter?
Evidence is mixed, with independent negligible-effect trials. Adequate nutrition and resistance training remain the foundation.
Should I pay more for free acid?
Faster concentration peaks do not establish better outcomes; calcium-salt AUC was higher in a newer study.
Can it help after surgery or during cancer treatment?
Clinical studies are promising but often use mixtures. The treating nutrition/medical team must decide; this is not a home recovery prescription.
How much and when?
The common research schedule is about 3 g/day, often split. Check whether the label means calcium-salt mass or HMB content; timing superiority is unestablished.
Stack interactions
- Caution Creatine [CAUTION // REVIEW]
A source mention of a senior combination trial has missing catalog metadata. Additive benefits in healthy trained adults remain unconfirmed; do not call this proven synergy. - Caution Arginine and glutamine [CAUTION // REVIEW]
Many clinical studies use all three ingredients. Their effects and safety cannot isolate HMB.
PMID 39765161 PMID 15080599 - Caution Glucose-lowering drugs [CAUTION // REVIEW]
No clinically established interaction is documented; monitoring is a theoretical precaution, not proof of hypoglycemia.
PMID 10917905 - Caution Immunosuppressants / clinical nutrition [CAUTION // REVIEW]
Liver-transplant waitlist and surgical studies do not establish unrestricted combination safety with immunosuppressants.
PMID 37099902 PMID 39765161
Red flags: interactions and who should avoid it
Interactions
No established clinically important drug interaction is documented. Glucose-lowering treatment warrants monitoring as a theoretical precaution. Clinical nutrition during cancer, transplantation or surgery needs clinician oversight; HMB plus arginine/glutamine results cannot be attributed to HMB alone.
Avoid or ask a doctor first if
Pregnancy, breastfeeding and pediatric safety are insufficient. Kidney/liver disease, cancer and perioperative use require the treating team. Trials in cirrhosis do not establish unrestricted use in all liver or kidney disease.
Sources (PubMed, 33)
- Effects of oral administration of β-hydroxy β-methylbutyrate on lean body mass in older adults: a systematic review and meta-analysis.
PMID 33034021 · 2021 · systematic review / meta-analysisReviews show small-to-moderate but heterogeneous lean-mass benefits in older or sarcopenic adults; strength and function respond less consistently.
- The Role of HMB Supplementation in Enhancing the Effects of Resistance Training in Older Adults: A Systematic Review and Meta-Analysis on Muscle Quality, Body Composition, and Physical Function.
PMID 41305674 · 2025 · systematic review / meta-analysisReviews show small-to-moderate but heterogeneous lean-mass benefits in older or sarcopenic adults; strength and function respond less consistently.
- The Effect of β-hydroxy-β-methylbutyrate (HMB) on Sarcopenia and Functional Frailty in Older Persons: A Systematic Review.
PMID 30697623 · 2019 · systematic review / meta-analysisReviews show small-to-moderate but heterogeneous lean-mass benefits in older or sarcopenic adults; strength and function respond less consistently.
- Effects of Beta-Hydroxy-Beta-Methylbutyrate Supplementation on Older Adults with Sarcopenia: A Randomized, Double-Blind, Placebo-Controlled Study.
PMID 37248756 · 2023 · randomized controlled trialReviews show small-to-moderate but heterogeneous lean-mass benefits in older or sarcopenic adults; strength and function respond less consistently.
- Effects of exercise and/or β-hydroxy-β-methylbutyrate supplementation on muscle mass, muscle strength, and physical performance in older women with low muscle mass: a randomized, double-blind, placebo-controlled trial.
PMID 34081113 · 2021 · randomized controlled trialReviews show small-to-moderate but heterogeneous lean-mass benefits in older or sarcopenic adults; strength and function respond less consistently.
- Supplementation with β-hydroxy-β-methylbutyrate after resistance training in post-acute care patients with sarcopenia: A randomized, double-blind placebo-controlled trial.
PMID 38171034 · 2024 · randomized controlled trialReviews show small-to-moderate but heterogeneous lean-mass benefits in older or sarcopenic adults; strength and function respond less consistently.
- A double-blind placebo controlled trial into the impacts of HMB supplementation and exercise on free-living muscle protein synthesis, muscle mass and function, in older adults.
PMID 30360984 · 2019 · randomized controlled trialReviews show small-to-moderate but heterogeneous lean-mass benefits in older or sarcopenic adults; strength and function respond less consistently.
- Oral Nutritional Supplement with β-hydroxy-β-methylbutyrate (HMB) Improves Nutrition, Physical Performance and Ameliorates Intramuscular Adiposity in Pre-Frail Older Adults: A Randomized Controlled Trial.
PMID 34179932 · 2021 · randomized controlled trialReviews show small-to-moderate but heterogeneous lean-mass benefits in older or sarcopenic adults; strength and function respond less consistently.
- Effects of Protein, Essential Amino Acids, B-Hydroxy B-Methylbutyrate, Creatine, Dehydroepiandrosterone and Fatty Acid Supplementation on Muscle Mass, Muscle Strength and Physical Performance in Older People Aged 60 Years and Over. A Systematic Review on the Literature.
PMID 29300431 · 2018 · systematic review / meta-analysisReviews show small-to-moderate but heterogeneous lean-mass benefits in older or sarcopenic adults; strength and function respond less consistently.
- The effects of 12 weeks of beta-hydroxy-beta-methylbutyrate free acid supplementation on muscle mass, strength, and power in resistance-trained individuals: a randomized, double-blind, placebo-controlled study.
PMID 24599749 · 2014 · randomized controlled trialA 12-week free-acid RCT reported large gains, while independent calcium-salt/free-acid trials found negligible strength and hypertrophy effects. Commercial affiliations are a material limitation.
- Negligible Effects of β-Hydroxy-β-Methylbutyrate Free Acid and Calcium Salt on Strength and Hypertrophic Responses to Resistance Training: A Randomized, Placebo-Controlled Study.
PMID 30859862 · 2019 · randomized controlled trialA 12-week free-acid RCT reported large gains, while independent calcium-salt/free-acid trials found negligible strength and hypertrophy effects. Commercial affiliations are a material limitation. Some early kinetic studies report faster peaks; faster peaks do not prove greater chronic efficacy, and newer AUC findings favor calcium salt. 100% denotes pure HMB free acid composition, not absorption. Include only declared HMB content, not the total gel or capsule mass.
- β-hydroxy-β-methylbutyrate free acid supplementation may improve recovery and muscle adaptations after resistance training: a systematic review.
PMID 29037326 · 2017 · systematic review / meta-analysisA 12-week free-acid RCT reported large gains, while independent calcium-salt/free-acid trials found negligible strength and hypertrophy effects. Commercial affiliations are a material limitation.
- β-Hydroxy-β-methylbutyrate free acid reduces markers of exercise-induced muscle damage and improves recovery in resistance-trained men.
PMID 23286834 · 2013 · randomized controlled trialSome trials lower CK, inflammatory markers or improve work-capacity recovery; another trial found no attenuation of damage. These acute markers do not prove chronic hypertrophy.
- Pre-exercise β-hydroxy-β-methylbutyrate free-acid supplementation improves work capacity recovery: a randomized, double-blinded, placebo-controlled study.
PMID 29420925 · 2018 · randomized controlled trialSome trials lower CK, inflammatory markers or improve work-capacity recovery; another trial found no attenuation of damage. These acute markers do not prove chronic hypertrophy.
- β-Hydroxy-β-methylbutyrate (HMB)-free acid attenuates circulating TNF-α and TNFR1 expression postresistance exercise.
PMID 23908318 · 2013 · randomized controlled trialSome trials lower CK, inflammatory markers or improve work-capacity recovery; another trial found no attenuation of damage. These acute markers do not prove chronic hypertrophy.
- Effects of β-hydroxy-β-methylbutyrate free acid and cold water immersion on post-exercise markers of muscle damage.
PMID 24639242 · 2014 · randomized controlled trialSome trials lower CK, inflammatory markers or improve work-capacity recovery; another trial found no attenuation of damage. These acute markers do not prove chronic hypertrophy.
- Exercise-induced muscle damage is not attenuated by beta-hydroxy-beta-methylbutyrate and alpha-ketoisocaproic acid supplementation.
PMID 20072045 · 2010 · randomized controlled trialSome trials lower CK, inflammatory markers or improve work-capacity recovery; another trial found no attenuation of damage. These acute markers do not prove chronic hypertrophy.
- Effects of β-hydroxy-β-methylbutyrate free acid and cold water immersion on expression of CR3 and MIP-1β following resistance exercise.
PMID 24500432 · 2014 · randomized controlled trialSome trials lower CK, inflammatory markers or improve work-capacity recovery; another trial found no attenuation of damage. These acute markers do not prove chronic hypertrophy.
- β-Hydroxy-β-methylbutyrate and its impact on skeletal muscle mass and physical function in clinical practice: a systematic review and meta-analysis.
PMID 30982854 · 2019 · systematic review / meta-analysisA clinical meta-analysis favors muscle-mass preservation more than strength/function; many cancer, bed-rest and surgical trials are combination nutrition studies.
- Resistance training and β-hydroxy-β-methylbutyrate for functional recovery in critical illness: a multicenter 2 × 2 factorial randomized trial.
PMID 41102810 · 2025 · randomized controlled trialA clinical meta-analysis favors muscle-mass preservation more than strength/function; many cancer, bed-rest and surgical trials are combination nutrition studies.
- The Effects of 12-Week Beta-Hydroxy-Beta-Methylbutyrate Supplementation in Patients with Liver Cirrhosis: Results from a Randomized Controlled Single-Blind Pilot Study.
PMID 34371806 · 2021 · randomized controlled trialA clinical meta-analysis favors muscle-mass preservation more than strength/function; many cancer, bed-rest and surgical trials are combination nutrition studies. Common study doses around 3 g/day are generally well tolerated; short-term safety cannot establish indefinite high-dose safety.
- Effects of β-hydroxy-β-methylbutyrate on skeletal muscle mitochondrial content and dynamics, and lipids after 10 days of bed rest in older adults.
PMID 28705993 · 2017 · randomized controlled trialA clinical meta-analysis favors muscle-mass preservation more than strength/function; many cancer, bed-rest and surgical trials are combination nutrition studies.
- The effect of β-hydroxy β-methylbutyrate (HMB) with nutritional counselling on anthropometric muscle mass markers, strength, functionality, and quality of life in patients on the waiting list for liver transplantation: A double-blind study.
PMID 37099902 · 2023 · randomized controlled trialA clinical meta-analysis favors muscle-mass preservation more than strength/function; many cancer, bed-rest and surgical trials are combination nutrition studies. Liver-transplant waitlist and surgical studies do not establish unrestricted combination safety with immunosuppressants.
- Effects of preoperative beta-hydroxy-beta-methylbutyrate, arginine, and glutamine supplementation on cardiac surgery: A randomized controlled trial.
PMID 39765161 · 2025 · randomized controlled trialA clinical meta-analysis favors muscle-mass preservation more than strength/function; many cancer, bed-rest and surgical trials are combination nutrition studies. Many clinical studies use all three ingredients. Their effects and safety cannot isolate HMB. Liver-transplant waitlist and surgical studies do not establish unrestricted combination safety with immunosuppressants.
- Supplementation with a combination of beta-hydroxy-beta-methylbutyrate (HMB), arginine, and glutamine is safe and could improve hematological parameters.
PMID 15080599 · 2004 · systematic review / meta-analysisA clinical meta-analysis favors muscle-mass preservation more than strength/function; many cancer, bed-rest and surgical trials are combination nutrition studies. Many clinical studies use all three ingredients. Their effects and safety cannot isolate HMB.
- β-Hydroxy-β-methylbutyrate as a countermeasure for cancer cachexia: a cellular and molecular rationale.
PMID 23919746 · 2013 · narrative reviewA clinical meta-analysis favors muscle-mass preservation more than strength/function; many cancer, bed-rest and surgical trials are combination nutrition studies.
- HMB supplementation combined with high-intensity functional exercise supports aerobic capacity but not strength in trained and untrained males: a randomized controlled trial.
PMID 42441818 · 2026 · randomized controlled trialOne small RCT of trained and untrained males reports aerobic-capacity support without greater strength; replication is needed.
- Effect of dietary supplements on lean mass and strength gains with resistance exercise: a meta-analysis.
PMID 12433852 · 2003 · systematic review / meta-analysisAn older commercially linked meta-analysis found small body-composition effects, including about 0.28% additional lean-mass gain per week; independent confirmation in trained adults is weak.
- beta-hydroxy-beta-methylbutyrate (HMB) supplementation in humans is safe and may decrease cardiovascular risk factors.
PMID 10917905 · 2000 · systematic review / meta-analysisCommon study doses around 3 g/day are generally well tolerated; short-term safety cannot establish indefinite high-dose safety. No clinically established interaction is documented; monitoring is a theoretical precaution, not proof of hypoglycemia.
- Comparison of availability and plasma clearance rates of β-hydroxy-β-methylbutyrate delivery in the free acid and calcium salt forms.
PMID 26373270 · 2015 · randomized controlled trialOlder studies favor faster free-acid peaks; a 2024 study found greater calcium-salt total exposure (AUC). Approximate composition: 1 g calcium salt contains 0.8 g HMB. The broad 2400-3000 mg HMB-equivalent interval reflects common 3 g salt versus 3 g HMB reporting; verify each paper, not a therapeutic target. Some early kinetic studies report faster peaks; faster peaks do not prove greater chronic efficacy, and newer AUC findings favor calcium salt. 100% denotes pure HMB free acid composition, not absorption. Include only declared HMB content, not the total gel or capsule mass.
- Free acid gel form of β-hydroxy-β-methylbutyrate (HMB) improves HMB clearance from plasma in human subjects compared with the calcium HMB salt.
PMID 21134325 · 2011 · randomized controlled trialOlder studies favor faster free-acid peaks; a 2024 study found greater calcium-salt total exposure (AUC). Approximate composition: 1 g calcium salt contains 0.8 g HMB. The broad 2400-3000 mg HMB-equivalent interval reflects common 3 g salt versus 3 g HMB reporting; verify each paper, not a therapeutic target. Some early kinetic studies report faster peaks; faster peaks do not prove greater chronic efficacy, and newer AUC findings favor calcium salt. 100% denotes pure HMB free acid composition, not absorption. Include only declared HMB content, not the total gel or capsule mass.
- Superior bioavailability of the calcium salt form of β-hydroxy-β-methylbutyrate compared with the free acid form.
PMID 38564019 · 2024 · randomized controlled trialOlder studies favor faster free-acid peaks; a 2024 study found greater calcium-salt total exposure (AUC). Approximate composition: 1 g calcium salt contains 0.8 g HMB. The broad 2400-3000 mg HMB-equivalent interval reflects common 3 g salt versus 3 g HMB reporting; verify each paper, not a therapeutic target. Some early kinetic studies report faster peaks; faster peaks do not prove greater chronic efficacy, and newer AUC findings favor calcium salt. 100% denotes pure HMB free acid composition, not absorption. Include only declared HMB content, not the total gel or capsule mass.
- Impact of the calcium form of β-hydroxy-β-methylbutyrate upon human skeletal muscle protein metabolism.
PMID 29097038 · 2018 · randomized controlled trialOlder studies favor faster free-acid peaks; a 2024 study found greater calcium-salt total exposure (AUC). Approximate composition: 1 g calcium salt contains 0.8 g HMB. The broad 2400-3000 mg HMB-equivalent interval reflects common 3 g salt versus 3 g HMB reporting; verify each paper, not a therapeutic target.
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