β-Hydroxy β-methyl butyric acid, more commonly referred to as just HMB, is a metabolite (byproduct) of leucine, the essential muscle-bulking amino acid that you’re probably familiar with if you regularly workout or hangout in weightlifting circles. HMB is proven to have an anabolic effect – meaning that it spurs muscle development.
Bodybuilders and other athletes often include HMB in their supplemental rotation due to its impressive clinical record of promoting muscle synthesis while preventing muscle breakdown.
People who augment their workouts with HMB see substantial gains in lean muscle mass and correlating increases in strength and performance. Additionally, HMB helps to mitigate the damage that muscles incur during intense weightlifting sessions, facilitating a speedier recovery and, ultimately, the opportunity for more reps in the gym.
In this article, we’ll discuss the science behind HMB’s muscle-building activities, how and when to take it, and any potential side effects associated with HMB supplementation for athletes.

What is HMB Supplementation Used For?
Next to other mainstays of gymgoers like creatine and protein powder, HMB is one of the most studied supplements for enhancing size and strength in bodybuilders and weightlifters.
Developers initially designed HMB as an emerging treatment for muscle-wasting diseases like cancer and HIV that trigger significant muscle loss. They also found impressive success using HMB as a counteractive agent against sarcopenia, the medical term for unhealthy muscle loss in the elderly.
However, in addition to treating disease, researchers quickly discovered the applications of HMB’s anabolic properties for athletes and otherwise healthy people looking for a boost in the gym.
Protein synthesis refers to the directed activity of protein creation to be used as enzymes, hormones, or, in the case of bodybuilders, to catalyze muscle tissue development following a workout.
Several factors affect how efficiently your body synthesizes proteins. The good news is that HMB supercharges protein biosynthesis, resulting in faster, bigger gains.
The evidence suggests that HMB promotes protein synthesis by spurring translation of genetic material into protein, a crucial initial phase in the formation of new protein cells.
HMB and Cardio
Although the word “cardio” is blasphemous to some in the weightlifting community, improving your cardiovascular capacity could translate into longer sets and, maybe, could mean the difference between hitting that last muscle-exploding rep or not.
Studies have proven that HMB increases the maximum oxygen consumption in the body – referred to as “VO2 max,” a critical marker of overall fitness. Elite athletes around the world tend to have significantly elevated VO2 maxes than non-athletes.
When Should You Take HMB?
As with any supplement, the age-old question becomes: when should I take it? Cue the pre vs. post-workout banter.
Because many of HMB’s benefits in terms of promoting muscle development stem from its activity in preventing “catabolism” – the state in which your body begins to break down muscle proteins for other purposes.
When you visit the gym on an empty stomach or while practicing a form of intermittent fasting popular among many athletes, you run the risk of triggering a catabolic state after you leave the gym.
Supplementing with HMB either immediately before or directly after a workout is the ideal time to take it. With this timeframe, you enjoy the added benefit of being able to consume it with your regular pre or post-workout shake.
What Forms Is HMB Available In?
HMB comes as a common ingredient in many popular pre and post-workout blends produced by industry leaders in fitness and performance supplementation. HMB can be found in:
• Creatine formulations.
• Protein Powders.
• NO Shots and Other Pre-Workout “pumps”
• Stand-alone powder (pure HMB).
Although buying HMB by itself and mixing it into your workout shake is an option, most people opt to more conveniently source their HMB from supplements like protein powders that include infusions of the leucine metabolite.
In addition to availability through supplementation, we do get small amounts of HMB through diet. Foods like avocados, alfalfa sprouts, grapefruit, and catfish contain significant quantities of HMB – however, only a small percentage of the HMB taken in through diet remains intact through digestion.
To fully reap the benefits of HMB for muscle-building, getting an adequate supply through diet would be virtually impossible. You need to use an HMB supplement from a reputable, third-party tested manufacturer to see the gains that you want on the squat rack or the bench press. Finding the best HMB supplements is very important to make sure it’s right for you.
How to Ensure a High-Quality HMB Product
Due to the FDA’s uneven regulation of dietary supplements, HMB and other gym products are not subject to the same strict quality control standards that pharmaceutical drugs are.
As a result, it’s ultimately up to you as the consumer to discriminate the quality supplements from the not-so-great. With this warning in mind, you should always purchase products that have been verified for quality by independent laboratories that can confirm that your supplement is, in fact, real HMB.
HMB Dosage
The general daily recommended dosage for a healthy adult using HMB for muscle gain is approximately 3 grams. Although you can split up the dosage if you like between two or more servings, there is no evidence that staggering dosages throughout the day are more effective at producing results than taking it all at once.
What are the side effects of HMB?
HMB has been thoroughly tested by medical groups around the globe for decades, and no significant dangers have been found to be associated with HMB use, even in large doses.
Because HMB is naturally occurring, it is completely legal in the US and abroad. Unlike other substances, testing for HMB would be virtually impossible in competitive sports. Furthermore, it is produced in the liver and sourced from the diet in moderate amounts, so it is totally safe for consumption.

Does HMB really work?
Is HMB really effective? Judging by the reams of scientific data on HMB from real research groups outlined here and widely available elsewhere on the web, we can safely say that HMB is one of the best-studied supplements for initiating muscle protein synthesis and, in turn, growing bigger and stronger muscles.
The Bottom Line on HMB as a Supplement
The jury is in: incorporating HMB supplementation into your daily routine is a proven, cost-effective, and worthy addition to your workout victuals. For maximum convenience, much respected protein powder and creatine formulation manufacturers include HMB as a standard ingredient.