The main side effects produced by oral eugenol are mainly related to drug overdose: 1. may cause rapid heartbeat. 2. may induce angina attacks in older patients. 3. may easily produce osteoporosis. However, the above side effects must occur when the dose of Eugenol is not adequately evaluated and Eugenol is replaced by an overdose. When the patient takes Eugenol orally to replace the thyroid function within the completely normal range, the above side effects will not occur. Therefore, patients with hypothyroidism are advised to regularly monitor changes in thyroid function and adjust the dosage of eugenol in a timely manner during the long-term oral administration of eugenol. In particular, if the patient’s rapid heartbeat may be caused by too much eugenol replacement, the thyroid function should be rechecked and the dosage of eugenol should be reduced if it indicates that the thyroid level is indeed elevated.