Patient could be having severe diarrhea, or just received chemotherapy. Lot of patients abusing alcohol have hypomagnesemia.
Usually found incidentally.
Check Mg level in all cases of severe hypokalemia. Mg needs to be corrected first before severe hypokalemia gets corrected.
Correct this or else it may be difficult to correct other electrolyte abnormalities.
Magnesium Sulfate 1mg IV X 1-2 doses.
Magnesium Oxide 400mg PO BID
Again, different hospitals have different formulary for supplementing Mg iv or PO.
Speak to other hospitalists or pharmacy for particulars in your hospital.