Deficiency Hypomagnesemia causes poor diet alcoholism poorly controlled diabetes presentation hyperexcitability muscle cramps tetany palpitations hypocalcemia may present with paresthesias, weakness, and muscle cramping can cause QT prolongation symptomatic hypocalcemia requires repletion hypokalemia may present with weakness, cramps, and U-waves on ECG refractory to potassium repletion diagnosis serum magnesium level does not always correlate with intracellular magnesium level replete if hypomagnesemia suspected Hypermagnesemia causes renal failure exogenous usage (preeclampsia, eclampsia) presentation apnea areflexia paralysis treatment stop giving magnesium calcium