Holland & Barrett Magnesium citrate is a combination of magnesium and citric acid. Citrates are readily absorbed into the blood stream via the pyruvate cycle. Magnesium also has several other functions, it contributes to electrolyte balance, normal energy yielding metabolism, normal functioning of the nervous system, normal muscle function, normal protein synthesis, normal psychological function and it also has a role in the process of cell division. Not intended for use by persons under age of 18.