It takes up to a day and a half to rehydrate a person who has a lost a mild to moderate amount of fluid. A longer period of time may be necessary for a person suffering from severe dehydration.
Symptoms from dehydration can be relieved within hours following treatment, but it takes longer for the body to recover lost fluids completely. People recovering from dehydration should rest in a cool place, prop up their feet and consume beverages designed to replenish fluids and minerals. Commercial drinks or home-prepared mixtures made from water, sugar and salt are acceptable for treating dehydrated adults.