Hypothyroidism is short for hypothyroidism, and the typical levothyroxine replacement dose for adult patients is 50 to 200 µg/d, with an average of 125 µg/d. The dose based on body weight is 1.6 to 1.8 µg/(kg-d). The goal of hypothyroidism treatment is to restore serum thyroid-stimulating hormone and thyroid hormone levels to within the normal range, requiring lifelong medication. The dose of treatment depends on the patient’s condition, age, weight and individual differences. A higher dose of approximately 2.0 µg/(kg-d) is required for children; a lower dose of approximately 1.0 µg/(kg-d) is required for elderly patients; the replacement dose in pregnancy needs to be increased by 30% to 50%; and a higher dose of approximately 2.2 µg/(kg-d) is required for patients after surgery for thyroid cancer. Patients with hypothyroidism should be treated with medication under the supervision of a medical professional.