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HMB Side Effects: A Comprehensive Analysis

Quick Summary

  • HMB (Hydroxymethylbutyrate) is a popular supplement for muscle growth.
  • Extensive studies show minimal negative side effects with recommended dosages (3g/day for up to 8 weeks, 6g/day over a month).
  • HMB is safe for long-term use in healthy adults, caution is advised for pregnant women & children due to limited research.
  • Calcium HMB, the common form of supplementation, poses no serious concerns at typical dosages.
  • Potential unlikely side effects include mild gastrointestinal distress & muscle cramps, which are usually temporary.
  • Staying hydrated & taking HMB with meals can help reduce any potential side effects.
  • Begin with a low dosage to assess tolerance & gradually increase.
  • Consult a healthcare professional before starting HMB supplementation for personalised advice.
  • Overall, HMB provides benefits for muscle growth & performance with low minimal risks.


Hydroxymethylbutyrate also known as HMB or β-Hydroxy β-Methylbutyrate is a popular supplement for advanced trainers looking at furthering their muscle growth. HMB is an extremely safe supplement to use, as you will see later, however, some people may be concerned about any potential side effects.

As such, here is a comprehensive guide looking at busting any myths regarding the side effects of HMB supplementation.

Does HMB have Side Effects?

  1. In short, several studies have shown next to no negative side effects of HMB use. The general recommended supplementation of 3g/day for up to 8 weeks has not resulted in negative changes in blood samples1.
  2. Similarly, a dose of 6g/day over a month also did not show any toxic or negative side effects on the body including blood profiles, liver function and kidney function2.
  3. A meta-analysis of HMB supplementation also found that the supplement was safe to take over extended periods of time3, especially in healthy adult males and females.
  4. However, No long-term studies have looked at the side effects on pregnant women & children, so these populations should treat the supplement cautiously.
  5. It should be noted though that a recent rodent study found a slight decrease in insulin sensitivity, however, this result has never been observed in human studies4.

Calcium HMB Side Effects

The most common form of HMB supplementation is in the compound calcium HMB, in which HMB is bound to a monohydrated calcium salt. Calcium is a mineral with fairly low toxicity and only extremely high levels over a long time can pose any serious concerns.

The amount in 3g or even 6g of Calcium HMB would not be enough to cause any serious concern as evidenced by many of the studies looking at the safety of HMB supplementation.

HMB Side Effects Long Term

As mentioned above, HMB supplements have been taken for a year at recommended dosages, without negative side effects. Further long-term studies would be ideal to support the initial studies.

HMB: Understanding Potential Minor Side Effects

While HMB is generally well-tolerated & very safe for most individuals, like any supplement, it may come with some "potential" side effects. These are noted following:

Gastrointestinal Distress

One of the most commonly reported side effects of HMB is mild gastrointestinal distress. This can include symptoms such as bloating, gas, or an upset stomach. These issues are typically temporary and tend to subside as the body adjusts to the supplement.

Muscle Cramps

In some cases, individuals may experience muscle cramps when taking HMB. This can be attributed to changes in electrolyte balance or dehydration. Ensuring proper hydration & electrolyte intake can help minimize the risk of experiencing muscle cramps.

Liver & Kidney Concerns

Some studies have suggested a potential link between high doses of HMB & liver or kidney issues. However, it's essential to note that these effects are very rare & are almost always associated with excessive HMB intake. Adhering to recommended dosage guidelines can significantly reduce the risk of any adverse impact on liver & kidney function.

Allergic Reactions

Though rare, some individuals may be sensitive or allergic to HMB. If you experience any signs of an allergic reaction, such as hives, difficulty breathing, or swelling, discontinue use immediately, and seek medical attention.

Mitigating Any Potential HMB Side Effects

Now that we've discussed the unlikely potential side effects, let's explore strategies to mitigate & minimise the risks associated with HMB supplementation.

Start with a Low HMB Dosage

To assess your tolerance & minimize the likelihood of side effects, start with a lower dosage of HMB. Gradually increase the dosage as your body becomes accustomed to the supplement.

Stay Hydrated

Maintaining proper hydration is essential when taking any supplement, including HMB. Drinking an adequate amount of water helps support kidney function & may reduce the risk of muscle cramps.

Combine HMB with Meals

Taking HMB with meals can aid in better absorption & reduce the likelihood of experiencing gastrointestinal distress. The presence of food in the stomach may buffer the supplement's effects & make it more tolerable.

Consult with a Healthcare Professional

Before starting any new HMB supplement regimen, one may wish to consult with a qualified healthcare professional. They can evaluate your health status, assess any potential contraindications or interactions with medications, & provide personalised recommendations.


In conclusion, HMB supplementation is safe & well-tolerated for most individuals, with minimal side effects reported. However, pregnant women & children should exercise caution. Stay hydrated, start with a low dosage, & consult a healthcare professional for personalised advice. Enjoy the benefits of HMB while prioritizing your well-being.

1. Nissen S, et al. beta-hydroxy-beta-methylbutyrate (HMB) supplementation in humans is safe and may decrease cardiovascular risk factors. J Nutr. (2000)
2. Gallagher PM, et al. Beta-hydroxy-beta-methylbutyrate ingestion, part II: effects on hematology, hepatic and renal function. Med Sci Sports Exerc. (2000)
3. Rathmacher JA, et al. Supplementation with a combination of beta-hydroxy-beta-methylbutyrate (HMB), arginine, and glutamine is safe and could improve hematological parameters. JPEN J Parenter Enteral Nutr. (2004)
4. da Justa Pinheiro CH, et al.: Metabolic and functional effects of beta-hydroxy-beta-methylbutyrate (HMB) supplementation in skeletal muscle. Eur J Appl Physiol 2012, 112:2531-2537.

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