A once common practice was to supplement the diet with potassium if one was taking a diuretic. However, some diuretics actually keep potassium in the body and supplementation could be a dangerous practice when used routinely with all diuretics. Carbenicillin, an antibiotic given by injection, has been associated with an increased risk of potassium deficiency. Infants and children are at most risk of deleterious accidental overdose with potassium. A meal could easily supply ten times the 100 milligrams considered prescription drug status.
Salt substitutes are exempt from the prescription requirement.
However, potassium is relatively safe because healthy kidneys maintain the body's potassium balance with extraordinary efficiency. Dietary intake of potassium in excess of 18,000 milligrams can cause high concentrations of the element in the blood, disturbances in heart and kidney function, and alterations in fluid balance. Blood levels of potassium can escalate as a result of excessive intake of salt substitutes that contain potassium, kidney failure, acidosis, major infections, hemorrhages in the gastrointestinal tract, and severe breakdown of muscle. Potassium is closely related to sodium in the regulation of blood pressure. The Merck Index , 12th edition, 1996.