Magnesium, calcium, and potassium are three of the four most abundant cations in the human body. A disturbance in any one may affect the other. In the case of refractory hypokalemia or hypocalcemia, the clinician should investigate for hypomagnesemia and treat if present, because repleting magnesium stores will likely facilitate corrections of the other electrolyte disturbances.

Concurrently low serum levels of potassium and magnesium are frequently seen in patients and are well documented in the literature. Studies have suggested that 42% of cases of hypomagnesemia are associated with hypokalemia and that hypokalemia itself may lead to excessive renal losses of magnesium. Although pediatric studies are limited, adult patients with low magnesium and potassium levels have a higher mortality rate than severity matched patients with normal magnesium levels. Possible etiologies of the excess mortality include cardiac dysrhythmias, coronary vasospasms, and cardiac arrests. The administration of magnesium can reduce arrhythmias and the mortality rate after adult myocardial infarctions by 25% to 74%. Additional medical studies suggest that efforts to maintain high-normal concentrations of magnesium will lead to a positive potassium homeostasis and less need for potassium infusions. This is important because magnesium infusions are considerably safer than infusions of potassium. Although rapid infusions of magnesium can lead to hypotension arrhythmia and flushing, potassium infusions have a significantly higher risk of cardiac dysrhythmia, phlebitis, pain, and tissue necrosis in the event of extravasation.