Under what conditions does mannitol crystallize? The clinical use of 20% mannitol injection is a supersaturated solution, the solubility of mannitol should be 18% under normal circumstances, 20% mannitol injection can easily precipitate crystals. Generally when the external temperature is below 20°C, 20% mannitol injection will precipitate crystals. In order to be used clinically, the storage temperature of mannitol injection is usually required to be above 20°C. Once crystallization occurs, hot water at about 80°C can be used to dissolve it before infusion into the body. In order to avoid crystallization of mannitol, it is also required that no other electrolytes be added to the mannitol infusion. The addition of other electrolytes makes it easier for mannitol to crystallize, which can have serious consequences. Therefore, the conditions under which mannitol will crystallize are as follows: 1. Supersaturated mannitol is prone to crystallization if it is infused at low temperatures, i.e. below 20°C. 2. When mixed with other electrolyte solutions, it is also prone to crystallization.