Hypokalemia, hyperkalemia, hyponatremia, hypernatremia, hypocalcemia, and hypercalcemia are commonly seen in emergency medicine. Severe abnormalities in any of these electrolytes can cause potentially life-threatening consequences to the patient. It is essential that the clinician understand and correct (if possible) the underlying cause of each disorder and recognize the importance of the rates of correction, especially with serum sodium disorders. The recommended doses in this article might have to be adjusted to the individual patient, and these modifications must be adjusted again to the pathophysiology of the primary underlying disorder.