HMB supplements: what the research shows

What is an HMB supplement?

An HMB supplement provides beta-hydroxy-beta-methylbutyrate, a compound your body makes from leucine, one of the amino acids in protein. Only about 5% of the leucine you eat is turned into HMB. The International Society of Sports Nutrition (ISSN) worked out that you'd need over 600 g of high-quality protein a day to make the 3 g of HMB used in most studies, which is why it's sold as a supplement.

There are two forms. Calcium HMB (often written HMB-Ca) is the one used in most research, and the free acid form (HMB-FA) is newer. The ISSN's 2025 position stand says the free acid form appears to raise blood HMB more, though recent results are mixed. HMB powder and HMB capsules contain the same compound; what differs is the form, the dose per serving and what else is in them.

What does the research on HMB show?

The answer depends on who took it. HMB has been studied in people for nearly 30 years, at doses from 1.5 to 6 g a day, and results differ a lot between groups.

People new to resistance training

The most consistent finding is a small strength benefit in people who haven't trained before. A 2009 meta-analysis of 9 studies with 394 young men found small gains in lower-body and overall strength in untrained lifters, but only trivial effects on body composition (Rowlands and Thomson). The studies lasted about five weeks on average.

Trained people

In people who already train, meta-analyses mostly find little or no effect. The same 2009 analysis found all strength effects in trained lifters were trivial. A 2018 meta-analysis of 6 trials in 193 trained and competitive athletes found no effect on strength, body mass, fat-free mass or fat mass (Sanchez-Martinez and colleagues). A 2020 review of 11 trials in adults aged 18 to 45 doing resistance training found a small increase in total body weight but no effect on fat-free mass, fat mass or strength, and concluded its findings don't support using HMB for those aims (Jakubowski and colleagues).

Older adults

Results in older adults are more mixed. A 2015 meta-analysis of 7 trials in 287 people aged 65 and over found greater muscle mass with HMB (Wu and colleagues). A 2021 analysis of 9 trials found HMB alone increased fat-free mass, but HMB added to exercise did not (Lin and colleagues). In a 2019 review of 15 trials in 2,137 people with illnesses that cause muscle loss, HMB, alone or in supplements containing it, gave small increases in muscle mass and strength, but no trial was at low risk of bias in every category (Bear and colleagues). Most recently, a 2026 meta-analysis of 13 trials in 561 adults aged 50 and over found HMB added nothing to resistance training for muscle mass, strength or fat mass, and concluded it can't be recommended as a routine add-on for people able to exercise (Wang and colleagues).

Across all groups, a 2025 umbrella review of 11 meta-analyses found small increases in muscle mass and strength with HMB and no change in fat mass, though it rated three of those meta-analyses as critically low quality (Bideshki and colleagues).

One small trial is often cited. Twenty-four healthy older adults spent 10 days on complete bed rest taking 3 g of HMB a day or a placebo; 19 could be assessed at the end. The placebo group lost about 2 kg of lean mass, while the HMB group's loss was close to zero after one participant was excluded, with no difference in physical function. The authors said a larger trial was needed (Deutz and colleagues, 2013).

The ISSN position stands on HMB, and their critics

The ISSN's 2013 position stand was strongly positive. It concluded that HMB can speed recovery by reducing exercise-induced muscle damage, that about 38 mg per kg of body weight a day (roughly 3 g for an 80 kg adult) can enhance muscle growth, strength and power in trained and untrained people with the right training, that it seems to work best when started two weeks before a hard bout of exercise, and that long-term use is safe (Wilson and colleagues). Its disclosures show one author conducted research for Metabolic Technologies, the company that sold HMB, and another advised Abbott Nutrition.

The 2025 update kept a positive line but softened some points. It says HMB may improve strength and power in untrained people, that benefits in trained athletes are mixed, and that HMB combined with exercise may help age-related muscle loss under select conditions (Rathmacher and colleagues). Its lead author is employed by MTI Biotech, previously worked at Metabolic Technologies, which until recently marketed HMB, and is named as an inventor on HMB patents. Commercial links don't make a review wrong, but several of the meta-analyses above found much smaller effects.

Some of the most positive data in trained people have also been questioned. In 2017, researchers Jeremy Gentles and Stuart Phillips pointed out inconsistencies between three papers from a single trial of free acid HMB in trained men, led by the same researcher who led the 2013 position stand. They included differences in the described supplement protocols and in control group numbers. The original authors replied that the papers were consistent and that the critics had misunderstood them.

Can HMB supplements make health claims in the UK?

No. Claims that HMB increases lean body mass, increases strength, aids recovery, reduces muscle damage or improves endurance were assessed by the European Food Safety Authority in 2011 and found not to be substantiated. They're listed as non-authorised on the Great Britain nutrition and health claims register. So this guide only reports what trials found. If an HMB product promises muscle growth or faster recovery on its label, it isn't using authorised wording.

Creatine and HMB together

Research on taking creatine and HMB together is thin. A 2019 systematic review found 6 studies of the combination, typically 3 to 10 g of creatine with 3 g of HMB for 1 to 6 weeks. Some found improvements in strength, short high-intensity (anaerobic) performance or body composition and others didn't, and none found benefits on markers of muscle damage or hormones (Fernández-Landa and colleagues). Creatine has the stronger case on its own: in Great Britain it has an authorised claim, increasing physical performance in successive bursts of short-term, high intensity exercise at 3 g a day. Our guide to how to take creatine covers the dose and timing.

How much HMB should you take?

Most studies used 3 g a day. The 2013 ISSN position stand suggested 38 mg per kg of body weight a day, split into two or three servings, while noting that the best dose and timing hadn't been properly studied. Check the label for how many grams of HMB a serving gives and which form it is, since a capsule product may need several capsules to reach 3 g. If you're comparing an HMB powder with capsules, work out the cost per 3 g of HMB.

Is HMB safe, and who should avoid it?

In the research so far, HMB appears to be well tolerated by healthy adults. The ISSN's 2025 position stand says the available data suggest it is safe for at least a year, and an earlier study found 6 g a day for a month had no effect on cholesterol, blood counts, blood glucose, or liver or kidney function. Long-term data beyond a year are limited.

Where Natura fits

Daily HMB, 3 g, is in the Natura cabinet (coming soon) as part of two sport packs: the Boxing Pack, with Daily Cherry 500 mg, and the Wrestling Pack, with Daily Electrolytes. HMB has no authorised health claims, so we make none for it.