Supplementation of HMB tends to be in the dosage range of 1–3 grams daily for the purpose of reducing muscle mass losses over time (anticatabolic). As HMB is said to be 20-fold more potent than leucine for this purpose, it is seen as equivalent to 20–60g of leucine supplementation.^[1]

HMB, a water-soluble metabolite of leucine, is excreted in the urine and is not reabsorbed by the kidneys back into the bloodstream. Studies have shown that approximately half of the supplemented HMB is lost through urine. Since the kidneys don’t reabsorb HMB, dividing the daily HMB dosage into three separate doses throughout the day may help to maintain steadier levels of HMB in the blood and thereby enhance its effectiveness.^[2][3]

For the purpose of muscle protein synthesis (MPS), HMB and leucine are fairly equivalent, although the latter (leucine) may be more potent on a per-gram basis. Supplementing with HMB is not advised for inducing muscle protein synthesis, since leucine is likely more effective as well as cheaper.

Supplementation of HMB prior to an exercise session to mitigate exercise-induced muscle damage would require the usage of an HMB free acid rather than a calcium salt, and the above dosage range still holds. For this specific purpose, HMB is to be taken 30–60 minutes before a workout when taking the HMB-FA form, or 60–120 minutes if taking the HMB-Ca form. On the other hand, when HMB is consumed in preparation for a potentially skeletal-muscle-damaging event (e.g., a competition), or prior to a high-intensity training bout for the purpose of reducing muscle damage, it appears to be more effective when taken regularly three times a day starting at least 2 weeks before the training period.^[4]