Subcutaneous (SC) injection is a technique for delivering drugs, vaccines, or biological agents into the subcutaneous tissue. The protocol involves selecting an injection site (e.g., dorsal neck, flank), cleaning the area with an antiseptic, and using a fine-gauge needle to insert at a 30–45° angle. The injection is administered slowly to ensure proper absorption. After withdrawal, gentle pressure is applied to prevent leakage. This method is commonly used in preclinical research and therapeutic applications due to its ease and sustained drug release.