A nurse is reinforcing teaching with an adolescent about self-administration of insulin. Which of the following instructions should the nurse include?

Rotating insulin injection sites is a fundamental principle of insulin self-administration for all patients, including adolescents. Consistent injection into the same spot causes lipohypertrophy — a buildup of fatty tissue that impairs insulin absorption and leads to unpredictable blood glucose control. Rotating within an anatomical region (e.g., abdomen, thigh, upper arm) and between regions helps maintain consistent absorption. Administering the medication at a 45-degree angle applies only in specific situations, such as when using longer needles or in very thin individuals with little subcutaneous tissue; current guidelines generally recommend 90-degree injection into a lifted skin fold for most patients using short pen needles, so this is not a universally correct instruction. Chilling the medication before administration is incorrect; cold insulin can be painful and is not recommended — insulin should be at room temperature before injection. Administering insulin into a muscle is dangerous; intramuscular injection causes faster, less predictable absorption and increases the risk of hypoglycemia. Insulin is a subcutaneous medication, not intramuscular. Understanding the rationale for site rotation and proper technique is essential for adolescents managing diabetes independently to achieve stable glycemic control.