Does HMB build or preserve muscle?
Probably not, if you already lift. In trials of lifters young and old, HMB added no extra muscle. But in one small trial, older adults on 10 days of bed rest lost almost none.
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Does HMB build muscle?
Probably not, if you already lift. HMB is something your body makes from leucine, an amino acid in protein foods. Only about 5% of leucine turns into HMB.
Two reviews tested it on top of weight training. In 302 people aged 18 to 45, it added a little body weight but no extra muscle or strength.
In 13 trials of adults aged 50 and over, it added no muscle, strength or fat loss. Those authors say it can’t be recommended as a routine add-on for people who can train.
| Who was studied | What trials found | Verdict |
|---|---|---|
| Lifters aged 18 to 45 | No extra muscle or strength. A little extra body weight. | No. |
| Lifters aged 50 and over | No extra muscle or strength across 13 trials. | No. |
| Older lifters, function tests | Maybe slightly better grip and a physical function test. No extra muscle. | Unclear. |
| People losing muscle through illness | Small gains in muscle and strength across 15 trials. | Not proven. |
| Older adults on 10 days of bed rest | Lost almost no lean mass. One trial of 19 people. | Not proven. |
Sources: Jakubowski 2020; Wang 2026; García-Alonso 2025; Bear 2019; Deutz 2013
Your next move: put your effort into training and protein first. See how to build muscle and what leucine does.
Can HMB preserve muscle when you can’t train?
Maybe. That’s the bed rest trial from the top.
Healthy adults aged 60 to 76, mostly women, stayed in bed for 10 days. Some took 1.5 g of HMB twice a day, starting 5 days before.
Source: Deutz 2013
One small trial is a hint, not proof. Only 19 people finished, and it was too small to show any difference in how well people moved. The authors say a larger trial must confirm it.
People losing muscle through illness also gained a little in 15 trials of 2,137 patients. Some trials mixed HMB with other nutrients. Every trial had at least one weak spot in how it was run, which makes the result less certain.
Laid up after illness or an injury? Ask your GP or care team whether it’s worth trying.
Losing weight on purpose? See how to keep muscle while you lose weight.
Why do some experts say HMB works?
A sports nutrition society, the ISSN, says HMB with training may improve body make-up at any age. It says HMB may help beginners gain strength, with mixed results in trained athletes.
Read the small print, though. Its lead author is named on HMB patents. The ISSN has also had grants from companies that sell HMB.
The reviews that found no effect in lifters came from separate teams. When they disagree, give more weight to the reviews whose authors don’t hold HMB patents.
Is HMB better than creatine or protein?
No. In adults under 50 who lift, creatine added 1.14 kg more lean mass than lifting alone. HMB added no clear extra muscle.
Where to spend your effort before HMB
- 1
Lift
Work all the major muscle groups on at least 2 days a week.
- 2
Eat protein
Get enough from food first.
- 3
Add creatine
Added 1.14 kg more lean mass in lifters under 50.
- 4
HMB last
If at all. No extra muscle in lifters.
Sources: NHS; Desai 2024; Wang 2026
Check your protein with how much protein you need a day. Then see how much creatine to take.
How much HMB should you take, and is it safe?
Trials often use 38 mg per kg of body weight a day.
The ISSN says 1.5 to 3 g a day looks safe for at least a year. Up to 6 g a day for 8 weeks caused no harm.
The bigger risk is the tub. UK Anti-Doping warns that supplements can be contaminated with banned substances, and labels can be wrong.
There’s no safety data for HMB in pregnancy, breastfeeding or children.
Before you buy HMB
- If you’re under 50 and want one muscle supplement, choose creatine over HMB.
- If you still try HMB, trials used 38 mg per kg of body weight a day, about 3 g at 80 kg.
- Keep to 1.5 to 3 g a day, the range the ISSN calls safe for at least a year.
- If you’re drug tested in sport, use only batch-tested products, as UK Anti-Doping advises.
Sources: NHS; Desai 2024; ISSN HMB; UKAD
Over 50 and feeling weaker? See the blood tests behind muscle loss before you buy anything.
When to speak to a GP
Book an appointment if:
- You keep losing weight without changing your diet or exercise routine. The NHS says to see a GP.
- You’re about to start strength training and haven’t exercised for some time, or you have medical conditions or concerns. The NHS says to speak to a GP first.
- You’re losing weight and have other symptoms too. The NHS says to see a GP as soon as possible.
Call 999 if one side of your face droops or you can’t lift both arms because one feels weak or numb. Also call if your speech slurs or you sound confused. These can be signs of a stroke, even if they stop.
Never stop or change a prescribed medicine without your prescriber.
Comparing every muscle supplement? See which supplements help build muscle.