Hydroxymethylbutyrate: Overview, Uses, Side Effects, Precautions, Interactions, Dosing and Reviews

Overview: Hydroxymethylbutyrate (HMB) is often used to help increase muscle mass, but its benefits are not well defined. Although it seems to be well tolerated, more research is needed to find out what side effects it may cause. HMB is available over the counter as a supplement, and many of these supplements may also contain other ingredients. Before taking HMB, make sure to tell your health care provider about any health conditions you have or medicines you are taking.

Uses

What is hydroxymethylbutyrate (HMB) used for?

Hydroxymethylbutyrate (HMB) is used to increase muscle mass in various situations, although its benefits are not well defined. Some common reasons people use HMB include the following.

• Age-related muscle loss (sarcopenia)
• Weight loss and muscle loss (wasting syndrome) in people with serious illnesses, such as cancer or AIDS
• To improve athletic performance and muscle strength

Note: The FDA has not reviewed HMB for safety and effectiveness. Learn more about dietary supplements here.

HMB is available as a dietary supplement in various strengths and dosage forms. It is often combined with other ingredients, such as creatine, vitamins, minerals, and amino acids.

How does HMB work (mechanism of action)?

Hydroxymethylbutyrate (HMB) is a substance that comes from leucine, an amino acid that occurs naturally in your body. Amino acids are building blocks for protein. Your body makes small amounts of HMB on its own, which helps your body build protein and muscle. There is interest in taking HMB to help boost athletic performance and build more muscle. But the benefits of HMB are not well defined, and taking HMB is not expected to increase muscle strength by a meaningful amount in healthy people who exercise regularly. There is also interest in taking HMB to help increase muscle mass in people who are prone to muscle loss, such as older adults and some people with serious illnesses, such as cancer or AIDS. When older adults or people with serious illnesses lose weight, they also tend to lose muscle mass. But most research shows that HMB does not increase muscle mass by a meaningful amount. More research is needed to know if anyone who is prone to muscle loss may benefit from taking HMB.

How should I store HMB?

You should store HMB according to the product label. Most dietary supplements should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight.

Side Effects

What are the most common side effects of HMB?

HMB seems to be well tolerated. But there is not enough research to know what the common side effects may be. Tell your health care provider if you have any side effects that bother you. There may be side effects of HMB that are not listed here. Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of HMB?

While less common, the most serious side effects of HMB are described below, along with what to do if they happen. Severe Allergic Reactions. HMB may cause allergic reactions, which can be serious. Stop taking HMB and get help right away if you have any of the following symptoms of a serious allergic reaction.

• Breathing problems or wheezing
• Racing heart
• Fever or general ill feeling
• Swollen lymph nodes
• Swelling of the face, lips, mouth, tongue, or throat
• Trouble swallowing or throat tightness
• Itching or skin rash
• Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
• Nausea or vomiting
• Dizziness, feeling lightheaded, or fainting
• Stomach cramps
• Joint pain

Warnings & Precautions

Who should not use HMB?

Allergies to Ingredients. People who are allergic to any of the following should not take HMB.

• Beta-hydroxy-beta-methylbutyrate
• Calcium beta-hydroxy-beta-methylbutyrate (CaHMB)
• Hydroxymethylbutyrate (HMB)
• Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific HMB products they stock.

What should I know about HMB before using it?

HMB is a dietary supplement. It cannot be marketed to treat or cure a disease. Read and follow the directions on the specific product you are taking, or take it as recommended by your health care provider. Keep HMB out of the reach of children. If you are using HMB powder, use an accurate measuring device to measure the powder, such as the device included with the product. Read the label carefully and measure the amount stated on the label. Supplements that contain HMB may also contain other ingredients, including amino acids, creatine, vitamins, and minerals. Read the product label carefully to see which ingredients it contains. Some of these ingredients may also be found in other supplements you are taking and the foods in your diet. Taking large amounts of some ingredients, such as vitamin D, may increase your risk for side effects. The FDA has not tested HMB products to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.

What should I tell my health care provider before using HMB?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if HMB is right for you. In particular, make sure that you discuss any of the following. Pregnancy. It is not known if or how HMB could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant. Breastfeeding. It is not known if HMB passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does HMB interact with foods or drinks?

There are no known interactions between HMB and foods or drinks. It is unknown if drinking alcohol will affect HMB.

Does HMB interact with medicines (drug interactions)?

There are no known interactions between HMB and medicines. Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. The interactions between HMB and medicines are not fully understood. As with most dietary supplements, the research on drug interactions with HMB is incomplete. Always check with your health care provider before taking HMB with any medicines.

Overdose/Missed Dose

What should I do if I accidentally use too much HMB?

If you or someone else has used too much HMB, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222. HMB may come in many different doses and forms, and some HMB supplements may also contain other ingredients. Read the product label closely and speak to a health care provider about how to take HMB safely. Do not take double or extra doses, even if you miss a dose.