Higher triiodothyronine may be caused by medication, primary hyperthyroidism, subacute thyroiditis, etc. It is recommended to consult a doctor in time. 1. Drug factors: patients with hypothyroidism need to take levothyroxine treatment, if the dose of the drug is too large, it may cause high triiodothyronine. 2. Disease factors: patients with primary hyperthyroidism may have high levels of triiodothyronine, accompanied by a decrease in thyroid stimulating hormone and an increase in total thyroid hormone and free thyroid hormone; subacute thyroiditis may have symptoms of hyperthyroidism in the early stages, which in turn leads to high levels of triiodothyronine. It is recommended to go to the hospital and ask the doctor to make a judgment if you have a high level of triiodothyronine, and it is not advisable to make a blind judgment on your own.