Universal diluent is a liquid used to dilute or reconstitute biological products, such as vaccines, serums, and antibodies. It is a sterile solution that typically contains salts and other compounds that help maintain the stability of the biological product and ensure that it is effective when administered. Universal diluent is used to prepare the biological product for administration, often by injection or infusion, and can also be used to wash and flush the injection equipment. It is called "universal" because it can be used with a variety of biological products that require dilution or reconstitution before administration. The specific composition of universal diluent can vary depending on the manufacturer and the type of biological product it is intended to be used with. It is important to follow the manufacturer's instructions and guidelines for the use of the diluent to ensure that the biological product is properly prepared and administered.