Low free thyroxine may be a sign of hypothyroidism, and the diagnosis needs to be made in conjunction with other indicators on thyroid function tests. In hypothyroidism, thyroid function tests may reveal low free thyroxine and total thyroxine, which may be caused by pituitary lesions, thyroid disease, low iodine intake, etc. It is recommended that the diagnosis be made in conjunction with other indicators in the thyroid function tests as well as clinical symptoms. In hypothyroidism, abnormal thyroid function may be detected in laboratory tests at an early stage, which may not be accompanied by obvious discomfort, or there may be symptoms such as chills, fatigue, slow heart rate, loss of appetite, hearing impairment, and less sweating. Patients with low free thyroxine are advised to seek prompt medical attention and actively cooperate with doctors to take relevant treatment measures.