Thyroid cancer is one of the common malignant tumors and its incidence has been increasing at a rate of 5% per year in recent years. Patients with post-operative thyroid cancer need to take oral levothyroxine tablets (i.e. Eugenol) after surgery. Eugenol can not only effectively prevent the recurrence of thyroid cancer after surgery, but also regulate the physiological functions of the thyroid gland. So when to take Eugenol and what dosage for post-operative thyroid cancer patients has been a troubling question for every post-operative patient! The initial dose is usually 50 micrograms, preferably taken every morning on an empty stomach, with a light diet one hour after taking the medication and avoiding high-protein and high-fat foods. If there are special diseases such as severe coronary heart disease, acute myocarditis, neuropathic headache, etc., the initial dose should be reduced by half and closely observed for any adverse reactions. If a patient misses a dose, the dose should be doubled on the second day, and the original dose should be restored on the third day. As the severity of the disease and the risk of side effects after taking Eugenol vary from patient to patient, the doctor will set different treatment goals, i.e. the range of TSH values to be achieved, taking into account the actual situation of the patient. Based on this goal, the patient needs to keep adjusting the dose of Eugenol until the target is reached. Patients are advised to go to the hospital every 4 weeks or so to measure TSH, which is used to decide whether to increase or decrease the dose of Eugenol; after reaching the target, thyroid function is rechecked every 2-3 months for 1 year, 3-6 for 2 years, and 6-12 months for 5 years to measure TSH to ensure that TSH is maintained in the target range. If Eugenol is not taken in sufficient quantity, the therapeutic effect will not be achieved. If Eugenol is overdosed, some clinical symptoms of hyperthyroidism such as insomnia, fever, arrhythmia and muscle weakness will occur. Patients need to give feedback on their symptoms to the doctor in time, and the doctor will arrange to check thyroid stimulating hormone (TSH) according to the actual situation of the patient. To ensure the accuracy of the test results, patients should take their original dose of medication early in the morning when the thyroid stimulating hormone blood test is measured. The thyroid stimulating hormone level is used to judge the adjustment of the dose of Eugenol.