HMB 101: Uses, Side Effects, Interactions, and Who It’s For

What Is HMB?

HMB stands for beta-hydroxy beta-methylbutyrate. Myprotein AU describes HMB as a chemical your body produces when it breaks down the amino acid leucine. iHerb AU’s NOW Foods HMB listing also describes HMB as a naturally occurring metabolite of leucine.

How much HMB the body produces from dietary leucine (typical percentages or amounts): Not specified on the source page.

Sources: Myprotein AU, iHerb AU (NOW Foods)

How HMB Works in the Body

Multiple allowed sources describe HMB primarily in the context of muscle protein balance:

• Myprotein AU states HMB is often used to slow down muscle protein breakdown. Source
• MyBrainCo describes HMB as supporting muscle protein balance and helping protect against muscle breakdown during intense training or reduced calorie intake (as stated on that page). Source
• NOW Foods’ HMB listing on iHerb AU states HMB plays a role in regulation of protein breakdown, helping preserve lean muscle tissue, and may help enhance recovery from intense exercise (as stated on that product page). Source

Specific biochemical pathways (e.g., exact enzymes, signalling pathways, or biomarker changes in humans): Not specified on the source page.

Key Benefits: What the Evidence Says

Important: Some statements below come from brand education pages and product listings. Where the source pages do not provide clear details (such as effect size, timeframes, or who responds best), this article uses “Not specified on the source page.”

1) Preserving lean mass by reducing muscle breakdown (most consistently described)

Myprotein AU explains HMB is commonly used to help slow muscle protein breakdown. iHerb AU’s NOW Foods HMB listing states HMB helps preserve lean muscle tissue by supporting regulation of protein breakdown.

How much lean mass is typically preserved, and over what timeframe, in different populations: Not specified on the source page.

Sources: Myprotein AU, iHerb AU (NOW Foods)

2) Muscle strength, mass, and recovery when paired with training

NOW Foods’ HMB listing on iHerb AU states HMB can help maintain muscle strength and mass when combined with regular exercise and a healthy diet, and may help enhance recovery from intense exercise. MyBrainCo similarly describes support for muscle strength, lean mass and recovery when combined with regular exercise (as stated on that page).

Whether HMB improves strength/mass outcomes in already well-trained athletes versus beginners: Not specified on the source page.

Sources: iHerb AU (NOW Foods), MyBrainCo

3) Active ageing and maintaining muscle as you get older (product-positioned)

Healthylife product pages position HMB (often combined with vitamin D3 and/or magnesium) in the context of maintaining muscle as you age. For example, the Bioglan Muscle Protect HMB + D3 listing says it supports muscle health as you age by maintaining muscle mass and muscle protein stores, and is suitable for those 50+. The Life Botanics Magnesium + HMB listing states HMB occurs naturally in the body and helps support muscle mass and muscle protein stores in ageing people (as stated on that page).

Clinical outcomes (e.g., measured changes in strength, mobility, or sarcopenia markers) for older adults using HMB: Not specified on the source page.

Sources: Healthylife (Bioglan), Healthylife (Life Botanics)

Who Might Benefit Most

• People increasing training intensity or volume: Myprotein AU notes research suggesting greatest benefit may occur with consistent supplementation before changing or intensifying training (as described on that page). Source
• People wanting support for lean mass retention during hard training or dieting phases: MyBrainCo describes HMB as supporting muscle protein balance and helping protect against breakdown during intense training or reduced calorie intake (as stated on that page). Source
• Adults focused on “active ageing” muscle maintenance: Healthylife listings position HMB + vitamin D3 products as supporting muscle mass/protein stores with age (as stated on those pages). Bioglan; Life Botanics

Whether HMB is appropriate for specific medical conditions (or as a substitute for clinical nutrition/rehab): Not specified on the source page.

Recommended Dosage and How to Take It

Dosage guidance varies by product form and brand. The most reliable approach is to follow your product label, and if you have a medical condition or take medication, confirm suitability with a clinician.

Evidence-discussion guidance (Myprotein AU):

• Recommended dosage: 3 g of HMB-Ca at least 1 hour prior to intense exercise (as described on that page).
• Loading approach: 1 g, 3 times a day for two weeks in the run up to a new training routine or higher intensity (as described on that page).
• HMB-FA (free acid) timing: 1–2 g, 30–60 minutes before exercise (as described on that page).

Label examples (iHerb AU product listings):

• Optimum Nutrition HMB: Suggested use states “take 3 capsules” (as shown on that listing). Source
• NOW Foods HMB 500 mg: Serving instructions and total daily dose: Not specified on the source page in the excerpted content available here (check the label section on-page). Source

Source: Myprotein AU

Best Time to Take HMB (Timing and With/Without Food)

Myprotein AU provides timing guidance based on form:

• HMB-Ca: 3 g at least 1 hour before intense exercise (as described on that page).
• HMB-FA: 1–2 g, 30–60 minutes pre-exercise (as described on that page).
• If taken with carbohydrates or as part of a meal: Myprotein AU states it may take longer to become available; if carbs are taken at the same time, consume HMB about 2 hours before training (as described on that page).

Whether HMB is better in the morning vs evening (or on rest days): Not specified on the source page.

Source: Myprotein AU

Forms and Quality: What to Look For on the Label

• HMB-Ca vs HMB-FA: Myprotein AU states HMB is sometimes combined with calcium (HMB-Ca) and other times sold as a “free acid” (HMB-FA), and notes most supplements on the market are HMB-Ca (as described on that page). Source
• Powder vs capsules: Myprotein AU says HMB supplements can be found in powdered or capsule forms (as described on that page). Source
• Stacking with creatine: Myprotein AU notes HMB is sometimes sold in combination with creatine due to similar additive effects (as described on that page). Source
• Check the per-serve dose: Use the supplement facts panel to confirm how many mg/g of HMB you get per serve, and how many serves are needed to match your target intake. Specific “best” dose for all users: Not specified on the source page.

Side Effects and Who Should Avoid It

Side effects, contraindications, and who should avoid HMB: Not specified on the source page.

Because HMB is used by many active adults and may be paired with other ingredients (e.g., vitamin D3, magnesium, creatine), always check the full ingredient list for allergens and suitability: Not specified on the source page.

Drug and Supplement Interactions

Drug interactions for HMB (including specific medications and monitoring needs): Not specified on the source page.

If you take prescription medication or have a medical condition, confirm HMB suitability with your pharmacist or GP.

FAQs

Is HMB the same as leucine?

No. Myprotein AU describes HMB as a chemical produced when the body breaks down leucine. iHerb AU’s NOW Foods listing describes HMB as a metabolite of leucine.

Sources: Myprotein AU, iHerb AU (NOW Foods)

What are the main forms of HMB in supplements?

Myprotein AU describes two main forms: HMB-Ca (calcium-bound) and HMB-FA (free acid). It notes most products are HMB-Ca, while some research suggests the free acid form may work more quickly (as described on that page).

Source: Myprotein AU

How much HMB do people commonly take?

Myprotein AU lists a recommended dosage of 3 g of HMB-Ca at least an hour before intense exercise, and describes a two-week loading approach (1 g three times daily) ahead of a new or more intense routine. Some product labels differ—e.g., an Optimum Nutrition HMB listing on iHerb AU suggests taking 3 capsules (exact grams per day depend on the label’s mg per capsule).

Sources: Myprotein AU, iHerb AU (Optimum Nutrition)

Is HMB only for athletes?

Not necessarily. Healthylife product pages position HMB + vitamin D3 products for muscle health as you age and maintaining muscle mass/protein stores, including suitability for those over 50 (as stated on those pages). That said, the best-fit use case for your situation: Not specified on the source page.

Sources: Healthylife (Bioglan), Healthylife (Life Botanics)

Optional: Shop HMB (placeholders)

[Browse HMB products on iHerb AU: https://au.iherb.com/c/hmb]

[Read: What is HMB and what does it do? (Myprotein AU): https://au.myprotein.com/blog/training/hmb-what-is-it-what-are-the-benefits/]

Disclaimer: This article is general information only and is not medical advice. If you are pregnant or breastfeeding, under 18, have a medical condition, or take prescription medication, speak with your GP or pharmacist before using supplements.

Sources (allowed domains only): Myprotein AU (HMB: benefits, forms, and dosage), iHerb AU (NOW Foods HMB 500 mg listing), iHerb AU (Optimum Nutrition HMB listing), MyBrainCo (Multi-Mag Hydrate – HMB description), Healthylife (Bioglan Muscle Protect HMB + D3 listing), Healthylife (Life Botanics Magnesium + HMB listing)