This research establishes the relationship between the influence of the stability of 6 magnesium compounds on their cellular uptake and focuses on the comparation between them, finding out which is the magnesium compound with the best bioavailability, depending on the stability. Mg2+ was dosed from tissues taken from various mice organs after the administration of compounds containing it, during the shelf life of the compounds, respectively at 6/12 months after their expiration. Different quantities of substances were also used � 25/50/100/200/300 mg/day/mouse, in groups of 2 mice for each dose. The samples were administered by gavage, following in parallel the possible side effects that may occur. During the shelf life of the compounds and at 6 months after expiration, in all organs, the lowest value was obtained for magnesium oxide and the highest value was detected for magnesium citrate. At 12 months after expiration, in all organs, the lowest/highest value was obtained in the case of oxide/orotate, respectively. It was found that the highest concentration of magnesium is stored in the spleen and lowest in lungs. The data obtained demonstrated a good stability of the tested substances (indicated by maintaining the cellular uptake rate) even 6 months after the expiration date.