Radioactive iodine (131I) therapy is a well established treatment modality for patient with hyperthyroidism and differentiated thyroid cancer after total thyroidectomy. Patients may sometimes need to be hospitalized to reduce radiation exposure of other people and relatives from radioactive patients receiving 131I therapy. This review was prepared to present suggestions and recommendations to health providers with reasoned instructions on radiation safety for patients, their families, caregivers, and the public after 131I therapy. The recommendations should help to ensure compliance and reduce the potential for harmful radiation exposure to others, and also to recognize that required actions may differ when attaining compliance with existing local regulations of other jurisdictions. Most of reported suggestions and recommendations are based on data derived from relevant measurements of radiation exposure, 131I clearance and excretion, and reports of the impact of precautions in limiting radiation exposure. We have quoted many descriptions from American Thyroid Association Guidelines in this review, which was published recently and emphasize the roles of the treating physician and the radiation safety officer in individualizing the precautions for each patient while allowing the referring physician to assist in preparing appropriate and adequate pre- and post-therapy actions. We tried to summarize the reported scientific papers and recommendations to provide general principle of radiation protection and some delicate issues in radiation safety after radioiodine therapy for the thyroid disease, to lower radiation exposure from patients to public and medical.