HMB
Nothing for trained lifters. A small gain in older adults.
Grade B: Some human proof
Small, early or mixed results in people.
The grade is for the use people talk about, not for every use. Filed under: Gym supplements.
How it works
A breakdown product of the amino acid leucine.
How it was given in studies
By mouth. In the trials people swallowed it as a capsule, tablet, powder or drink.
This is what the studies did. It is not a how-to.
What studies saw
A review of 6 trials in 193 trained athletes found no effect on strength or body composition. A review of 7 trials in adults over 65 found a small gain in muscle mass.
The trade-off
When added to strength training in older adults, a 2025 review of 10 trials found no clear gain in lean mass or walking speed.
When it showed up, in studies
Trial lengths varied. No clear timeline.
Sources
Put this grade on your site
Copy the line below. The badge links back to this page, so readers can check the sources. It grades the compound in studies. It does not rate any product or seller.
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Keep going
We show what studies found. We never tell you what to take. Doses vary by study. Check the sources and talk to a doctor.