Dietary modification is an inefficient and calorically unwise means of preventing hypokalemia; potassium supplements present compliance problems and are of little or no use in the patient with a concomitant magnesium deficiency. Prescribing potassium-sparing diuretics is the best prevention-oriented choice, but diabetics and older patients must be monitored for signs of hyperkalemia, and it is generally better not to use these agents in patients who are also taking ACE inhibitors.