Hypomagnesemia is a common entity in the inpatient and outpatient setting. in previous retrospective study hypomagnesemic patients have higher mortality and longer hospitalization. whether hypomagnesemia is merely a marker of poor prognosis, or whether replacing it can improve outcomes is unclear. The current standard of care is to discharge these patients without workup or further treatment, even if patients had received intravenous therapy while hospitalized. The investigator wish to examine prospectively whether giving replacement therapy affects mortality, length of hospital stay and overall well-being. In order to replete intracellular levels and replete magnesium stores, magnesium should be given for several months.