Hydroxymethylbutyrate (HMB): Benefits, Risks, & More

Hydroxymethylbutyrate (HMB): Benefits, Risks, & More

Hydroxymethylbutyrate (HMB) is a substance naturally produced in small amounts when your body breaks down the amino acid leucine. HMB works to help repair the structure and function of your muscles.

HMB is available in small amounts in some foods, such as grapefruit, alfalfa, and catfish, and as a dietary supplement. This supplement is most often used by athletes and bodybuilders to improve athletic performance. Older adults might also use HMB supplements to help slow the progressive loss of muscle mass.

Other names for HMB include:

  • Beta-hydroxy beta-methylbutyrate monohydrate
  • Beta-hydroxy-beta-methylbutyric acid
  • Calcium beta-hydroxy beta-methylbutyrate monohydrate

Here’s what you need to know before taking an HMB supplement, including its benefits and risks.

Hydroxymethylbutyrate (HMB) is a supplement popular among athletes and older adults because of its supposed benefits for muscle health. However, research on HMB’s effectiveness is mixed. Additional studies are needed to confirm its benefits, especially since current studies are small and usually involve only athletes. 

Improves Muscle Strength and Function

Several studies have reported multiple benefits of HMB supplementation on muscle performance, including increased aerobic activity, lean body mass, and ability to lift heavier weights.

For instance, one six-week study evaluated the supplement’s effects on muscle strength and power among adults participating in resistance training. For the study, 16 men took 1 gram (g) of either HMB or a placebo (a capsule with no HMB) three times daily. Those who took the HMB supplement saw an increase in the maximum weight they could lift at least once using the bench press and leg press. Additional studies and larger sample sizes are needed to confirm this benefit.

Researchers think HMB can help increase muscle strength and performance by regulating muscle protein metabolism, reducing body fat, and reducing the time it takes for muscles to recover after exercise.

May Improve Endurance

Taking HMB could increase your endurance. This could be because of its effect on lactate.

Lactate is a substance your body produces when muscles and red blood cells break down food for energy. At higher levels, lactate can decrease your ability to perform physical activities such as resistance training for longer periods of time. HMB may reduce the amount of lactate in your body, allowing you to perform for longer. This is critical for professional athletes and bodybuilders who train for competitive events.

One study showed that adults who took 3 g of HMB per day for 2-12 weeks significantly improved their endurance performance compared with those who took a placebo.

HMB might enhance athletic endurance even more if taken in combination with another supplement, such as creatine. Similar to HMB, creatine may decrease the amount of lactate in the body.

In a 10-week trial, researchers studied the physical performance of 28 elite male rowers. At the end of the trial, those who took a combination of HMB and creatine monohydrate had a greater increase in endurance capacity than those who took either supplement alone. 

Reduces Exercise-Induced Muscle Damage

Research shows HMB is effective in reducing muscle damage caused by intense exercise.

People with exercise-induced muscle damage may experience the following:

  • Decreased maximum strength
  • Decreased range of motion
  • Increased duration of muscle soreness
  • Increased inflammatory enzymes, such as creatine kinase and lactate dehydrogenase

HMB might help you recover faster from exercise and avoid the side effects of exercise-induced muscle damage by reducing the inflammation caused by resistance training and intense exercise. 

A small six-week study looked at the effects of HMB on exercise-induced muscle damage after long-distance runs. Sixteen participants ran 48 kilometers (nearly 30 miles) a week while taking 3 g of HMB or placebo daily. At the end of the trial, runners taking HMB saw a decrease in inflammatory enzymes usually present after muscle damage.

People who lift weights might also experience less muscle damage. A three-week study observed the effects of 1.5 g or 3 g of daily HMB supplementation on college students who had no regular physical training but were participating in free-weight training. Students taking the HMB supplementation had reduced levels of the inflammatory marker creatine kinase.

Researchers of another study evaluated the effects that taking 3 g of HMB daily for two or four weeks could have on muscle damage after lifting weights among 28 males who don’t normally exercise. Those who took the HMB supplement experienced increased muscle strength and range of motion with decreased muscle soreness and stiffness.

May Slow Down Muscle Wasting

Research shows that HMB may be effective in slowing down the loss of muscle mass and strength reductions in older adults with sarcopenia (gradual loss of muscle mass due to aging). HMB supplementation may help slow the progression of sarcopenia by increasing lean body mass and reducing muscle protein breakdown.

In a study of 34 active older adults aged 60 or older with sarcopenia, those taking HMB saw a positive effect on their muscles. After the 12-week trial, the adults had increased handgrip strength and walk speed, which are usually affected by sarcopenia. They also had a decrease in inflammatory enzymes known to worsen muscle damage.

Many of these studies involve a small sample size, so additional studies are needed to confirm this effect. It’s also unknown if older adults with sarcopenia who are not active would experience the same benefit of HMB supplementation.

HMB may also be effective in people with cachexia (muscle loss due to an illness like cancer). A systematic review of 15 studies, including more than 900 participants, suggests HMB supplementation may benefit adults with cancer. Participants who took HMB had:

  • Less muscle mass loss
  • Improved quality of life
  • An increase in their handgrip strength (signaling increased muscle function)

However, most results were mixed, so additional studies are needed to determine the full effects of HMB in this population.

HMB is available in two forms:

  • HMB Ca: The most basic form, which contains 400 milligrams (mg)—around 13%—of supplemental calcium (Ca)
  • HMB FA: The free acid form, a newer form that is absorbed in your body four times faster than HMB Ca

Both formulations are water-soluble, meaning they are flushed out of your body through your kidneys. HMB supplements are available for use in the form of capsules, powders, and tea sachets (bags). They can be easily purchased online, in retail pharmacies, and in vitamin stores.


It’s important to talk with your healthcare provider before starting any supplement. Because there’s no standard dosage for HMB, it’s best to take it as directed by the manufacturer. Most research involved people taking 1.5-3 grams of HMB daily, usually divided over two or three doses. However, according to one review, the most effective dosage of HMB is between 1-3 grams daily.

How and when you take HMB supplements may be based on the intended benefit. For example, if your goal is to reduce your recovery time after an intense workout session, you’ll want to take the supplement 30-60 minutes before starting your workout routine. Research supports taking the free acid form, HMB FA, 30 minutes before working out. However, if you prefer the HMB Ca form, you should take it 60 minutes before exercise since it’s not absorbed as quickly as the HMB FA supplement.

The International Society of Sports Nutrition (ISSN) suggests starting your HMB supplement of 3 g a day at least two weeks before starting high-intensity interval training (HIIT) to maximize the protective effects of the supplement on your muscles. 

Discuss with your healthcare provider which dose and formulation may best suit you based on your needs and goals.

HMB is considered safe when taken up to 3 g a day for 3-8 weeks. Experts haven’t agreed on the safety or effectiveness of taking this supplement longer than eight weeks, though research supports using it for up to 10-12 weeks. The ISSN considers it safe for long-term use in young and older adults.

HMB is not recommended for people who are pregnant, trying to become pregnant, or are breastfeeding. No studies support use in these populations.

Potential Drug Interactions

There are no reported drug interactions with HMB. However, some HMB supplements contain other ingredients such as creatine, vitamins, and amino acids.

Make sure you read the package labels to confirm there are no ingredients that may interact with other medications you take You can ask a pharmacist to help you check for these potential drug interactions.

What To Look For

Dietary supplements aren’t regulated like prescription and over-the-counter medications. To ensure quality, some manufacturers choose to have their products tested by a third party. These third-party companies make sure supplements contain only what’s listed on the label and are free of impurities or banned substances.

Check the labels for third-party certifications such as:

  • NSF’s Certified for Sport program
  • Informed Choice
  • Banned Substances Control Group (BSCG)

Stay away from supplements that claim to cure or treat conditions. Instead, look for statements that note the supplement “may help” certain health concerns or “‘is not intended to diagnose, treat, cure, or prevent disease.” These are signs the company is not making promises it cannot keep.

Can You Take Too Much HMB?

Since it’s not known how much HMB is too much to take, it’s best to follow the instructions on the label or as discussed with your healthcare provider. 

Some research has looked into higher doses—up to 6 g of HMB a day. While the participants didn’t experience any negative effects on their cholesterol, blood sugar, liver function, or kidney function with this higher dose, it is unclear which symptoms would signal that you’ve taken too much HMB. Taking higher levels of HMB is probably not much better than taking 3 g a day anyway, so you can avoid the risk of taking too much HMB by keeping your dose low.

HMB is generally well-tolerated. Most studies didn’t report many side effects. However, high blood pressure (hypertension), itching, and increased urination have been reported in one or two cases. Stomach pain, constipation, gas, heartburn, and nausea have also been reported, though these effects are rare.

HMB (hydroxymethyl butyrate) is a popular dietary supplement used by athletes and bodybuilders. It is effective in increasing athletic performance and reducing muscle breakdown after intense physical activity. Older adults may also use it to help reduce the effects of muscle loss due to aging or illness. Additional studies are needed to determine its effect on increasing muscle mass.

HMB is relatively safe to use, with side effects rarely reported. Before starting any new supplement, including HMB, speak to your healthcare provider.

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