Dehydration is the excessive loss of body fluid, accompanied with electrolyte disturbances. There are three types of dehydration: hypotonic or hyponatremic (primarily a loss of electrolytes, sodium in particular), hypertonic or hypernatremic (primarily a loss of water), and isotonic or isonatremic (equal loss of water and electrolytes). Isotonic dehydration is the most common form of dehydration.