While general recommendations are for 300-mg magnesium intake a day, an advanced low-dose formulation of magnesium chloride, ChronoMag (R), was designed to provide 100mg of magnesium element, thus decreasing the risk of gastrointestinal side effects and allowing long-term supplementation in health conditions related to low magnesium levels. The present study aimed to compare magnesium release profile and bioavailability between this patented low-dose continuous-release magnesium chloride tablet (100mg magnesium element) and a reference tablet at the usually prescribed dose (300mg magnesium element). Magnesium release profile was determined by dissolving the tablets in solutions simulating the gastrointestinal tract environment. A randomized double-blind crossover controlled trial of ChronoMag (R) versus reference tablet (3x100mg magnesium element tablets) in 12 normo-magnesemic healthy volunteers was conducted to evaluate the bioavailability of the patented magnesium chloride tablets (two 50mg magnesium tablets, once-a-day intake). While the reference tablet released 100% of its magnesium within 1h of dissolution, release from the magnesium chloride formulation was continuous for 6h. Cumulative urinary magnesium levels compared to those with the reference tablet were 76% (0-5h), 89% (0-10h), and 87% (0-24h). Elimination after 24h was fairly similar with both supplements. Our results suggest that the new magnesium chloride formulation, providing continuous low-dose magnesium release throughout the gastrointestinal tract, improves absorption and bioavailability. This formulation conforms to the physiological mechanism of magnesium absorption throughout the digestive tract, allowing high absorption, and may improve gastrointestinal tolerance in long-term use.