Fluid expansion therapy is a treatment to maintain fluid balance by supplementing certain fluids. Commonly used fluids are broadly categorized into: non-electrolyte fluids and electrolyte fluids. The former can replenish fluids lost through respiration, skin evaporation and urination to correct the hypertonic state of body fluids and prevent dehydration. You can drink mineral water, intravenous input of 5% to 10% glucose injection; and electrolyte fluids include isotonic sodium-containing fluids, such as saline, Ringer’s solution, modified Darrow’s solution and so on. The purpose of fluid expansion therapy is to correct the hypotonic state of body fluids and the disturbance of acid-base balance, and to replenish the loss of body fluids. In the presence of the need for fluid replacement and dehydration, it is necessary to seek medical attention as soon as possible to avoid delay in treatment.