If only T3 is low in the thyroid function test, and the rest of the indicators, such as TSH and T4, are in the normal range, it is considered that there is hypothyroidism, which means that thyroid function abnormalities can occur if you are in the more serious period of certain diseases. However, there is no need for medication for the time being. After the condition is stabilized, the thyroid function can be rechecked, and most of them can be restored to normal. Because TSH is the most sensitive of these indicators of thyroid function, if only T3 is low and the rest of the indicators are normal, it is recommended to follow up regularly, and there is no special drug treatment.