Hashimoto’s thyroiditis does not usually lead to diabetes, but it may be associated with diabetes, especially type 1 diabetes, which is an autoimmune disease. Hashimoto’s thyroiditis is a chronic autoimmune disease, the cause of which has not been fully clarified. It is considered to be the result of a combination of genetic, immune, and environmental factors, and can cause goiter and hypothyroidism symptoms, such as fatigue, chills, cold, bradycardia, loss of concentration and memory, muscular and joint pains, abdominal distension, constipation, and menstrual abnormalities. Hashimoto’s thyroiditis does not usually cause diabetes mellitus directly, but it may be accompanied by diabetes mellitus, especially type 1 diabetes mellitus, which is an autoimmune disease. Patients with Hashimoto’s thyroiditis who experience abnormal blood glucose values are advised to visit a hospital and ask their doctor to make a judgment and identify the cause.