HMB is made in the body from the amino acid leucine. It is used to protect muscle, in training and in older age.
Calculator Official intake Study doses Best form Safety Sources
This is not an essential nutrient, so there is no official daily intake. Only study doses are shown.
These are doses tested in research, not personal advice. Some exceed the upper limit because they were short courses or given under medical care.
38 mg per kg of body weight a day
ISSN position stand: 38 mg per kg of body weight a day with exercise training may improve body composition (more lean mass and/or less fat). Calcium HMB and the free acid form are both safe for at least a year.
No single dose
Meta-analyses in older adults found more muscle or fat-free mass with HMB than without (7 trials, 287 people; 9 trials, 448 people). In the newer one, HMB alone helped but HMB added to exercise gave no extra muscle.
No clear winner
HMB (calcium HMB or free acid), as on the label (g) (a good choice among equals)
Why: Both calcium HMB and the free acid form have been studied. The free acid may reach the blood faster, but results are mixed.
Only tiny amounts in food (citrus, catfish, alfalfa).
No important interactions known.
Studies up to a year found no safety problems, including for blood sugar control.
Pregnant, breastfeeding, on medication, or managing a health condition? Check with a doctor or pharmacist before starting a supplement.
Values checked: November 12, 2026.
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