Hyperthyroidism is related to glycated hemoglobin and may lead to elevated levels of the latter. Hyperthyroidism, or hyperthyroidism, is a thyrotoxic condition caused by excessive production of thyroid hormone by the thyroid gland itself. The main role of thyroid hormone is to promote the metabolism of substances and energy; it accelerates the absorption of glucose by the intestinal mucosa, increases the utilization of sugar by peripheral tissues, and has an accelerating effect on both the synthesis and breakdown of glycogen. Therefore, it may cause elevated blood glucose. In addition, glucocorticoids may be applied in the treatment of hyperthyroid crisis or thyroid-related ophthalmopathy, which may also cause elevated blood glucose. Glycosylated hemoglobin is a product of the combination of blood glucose and hemoglobin and is primarily used to screen the level of glycemic control over the last 2 to 3 months. Hyperthyroidism and some therapeutic medications can cause transient or even prolonged elevations in blood glucose levels, with a corresponding increase in glycosylated hemoglobin. It is important to note that diabetic patients also have elevated glycosylated hemoglobin and it is advisable to consult a physician to determine if diabetes is also present. It is recommended that the necessity of the test and its correlation with the underlying disease be analyzed on an individual basis by a medical professional.