Basically, electrolytes are substances which at least to some extent are present in the shape of ions. The important electrolytes are consequently either acids, bases, or salts.
The most important ions of biological electrolytes are sodium, potassium, calcium, magnesium, chloride, phosphate, and hydrogen carbonate. They are necessary in order to maintain the balance between the extracellular and the intracellular milieu. They influence and/or thus regulate the water balance in the body and the pH value of the blood. Electrolytes also play a central part in muscle and nerve cells.
They are administered orally and then taken up by the bowel system. Transpiration and energy consumption (work) remove them from the body, surpluses are excreted via the kidneys. The electrolyte balance is controlled by the action of hormones.
Diarrhea and vomiting lead to excessive fluid losses and hence losses of electrolytes. This results in a disturbance of the electrolyte balance. Such losses must be compensated for by so-called “electrolyte solutions” which contain the ions mentioned above and additionally rapidly available energy carriers like dextrose.