Final answer:
The nurse instructs a patient with diabetes on self-administration of insulin, applying Orem's theory, which focuses on patient self-care in disease management.
Step-by-step explanation:
The nurse utilizing a theory to teach a patient with diabetes how to self-administer insulin is most likely applying Orem's theory of self-care. This theory emphasizes patients' ability to perform self-care and thereby manage their health and wellness. Dorothea Orem's self-care deficit nursing theory is particularly relevant in the case of a patient with diabetes.
The theory identifies when nursing is needed and categorizes it as wholly compensatory (nurse does all for the patient), partly compensatory (nurse and patient share responsibility for care), or supportive-educative (patient independently carries out care). In this scenario, the nurse is engaging in the supportive-educative approach by teaching the patient to administer insulin, which is a critical self-care activity for managing diabetes.