Adverse Reactions: Adverse reactions are generally unlikely if the drug is taken as prescribed and monitored for clinical and laboratory indications. If the individual’s tolerated dose is exceeded or if the dose is overdosed, especially due to rapid dose increases at the beginning of treatment, the following clinical signs of hyperthyroidism may occur: tachycardia, palpitations, arrhythmias, angina pectoris, headache, muscle weakness and cramps, flushing, fever, vomiting, menstrual disorders, tremor, restlessness, insomnia, excessive sweating, weight loss, and diarrhea. In the above cases, the patient’s daily dose should be reduced or discontinued for a few days. Once the above symptoms have disappeared, the patient should carefully restart the medication. Hypersensitivity reactions may occur in some hypersensitive individuals. Contraindications: Those who are highly hypersensitive to the product and its excipients. Untreated adrenal insufficiency, pituitary insufficiency and thyrotoxicosis. Treatment with this product should not be started during acute myocardial infarction, acute myocarditis and acute allodynia. Precautions: 1. Use with caution in elderly patients. Start with small doses and increase the dose slowly. Thyroid hormone status should be monitored. Check every 3 months to determine dose increase of 12.5 μg/d or 50 μg/d based on TSH, T3 and T4 levels. 2. In patients with combined coronary artery disease, heart failure or tachyarrhythmia, all methods must be utilized to avoid mild hyperthyroid symptoms caused by levothyroxine. Therefore, patients with a history of heart disease need not be treated with caution. The starting dose of replacement therapy should be 25 μg/d, increasing by 25 μg every 8 weeks until blood TSH levels fall to normal. If a patient develops angina symptoms for the first time after starting treatment, consideration should be given to discontinuing replacement therapy while closely monitoring follow-up cardiac disease. If worsening angina symptoms are present, discontinue immediately and reevaluate and treat for cardiac disease. 3. In hypothyroidism secondary to pituitary disease, it must be determined whether there is a combination of adrenocortical insufficiency, and if present, glucocorticoid therapy must first be administered.