Electrolytes are minerals found naturally in the body, such as potassium, calcium, sodium, and magnesium. Electrolytes are needed to keep the body's balance of fluids at the proper level and to maintain normal functions, such as heart rhythm, muscle contraction, and brain function.

If the body's electrolytes are not in proper balance, a person may have seizures, an irregular heartbeat, muscle weakness, and other problems. Electrolyte imbalances can be caused by a variety of health conditions, such as chronic heart or kidney disease, endocrine diseases (such as problems with the adrenal, pituitary, thyroid, or parathyroid glands), eating disorders, or bone disorders. Any condition that causes the body to lose too much water (such as diarrhea, vomiting, fever, or taking medicines called diuretics) can also lead to an electrolyte imbalance.

An oral rehydration solution (ORS) that contains the right balance of electrolytes can be helpful for people who have diarrhea or vomiting, or for athletes who compete in endurance events (such as long-distance cycling or running races). An ORS can come as a liquid that is ready to drink, or as a powder that needs to be mixed with a certain amount of water before drinking. ORS examples include Hydralyte and Pedialyte.