An isotonic solution is a solution whose osmotic pressure is equal to that of plasma. An isotonic solution is a solution whose osmolality is equal to the osmolality of plasma, such as 0.9% NaCl solution and 5% dextrose solution. Under normal conditions, the osmotic pressure inside and outside the cell is approximate. The balance of intra- and extracellular osmolality relies on the movement of water between the inside and outside of the cell; when the osmolality of the extracellular fluid is high, water flows from the inside to the outside of the cell, and conversely, from the outside to the inside of the cell. Normal plasma osmolality is 280-320 mOsm/L, with plasma crystals such as Na+ and Cl- contributing more than 80% of the osmolality. Equal to the plasma osmolality is an isotonic solution, which can maintain the normal morphology of red blood cells; higher than the plasma osmolality is a hypertonic solution, which can cause the red blood cells to crumple; and lower than the plasma osmolality is a hypotonic solution, which can cause the red blood cells to swell and hemolysis to occur. It is recommended that patients go to regular hospitals for consultation and infusion of fluids under the guidance of specialists.