It's called Levothyroxine and I wouldn't ask except that the side effects sound scary, I am VERY prone to even remote side effects, and I have to HAVE to take thyroid medications...I have a hypothyroid and don't feel like getting diabetes I, heart disease, angina etc. by not taking it. But the side effects include choking, chest pains, trouble breathing...yada, yada, yada. Anyone else take this who is sensitive to medications and prone to side effects and did ok? Every time I take a new medication I have to worry about this!!!!! Grrrrrrrrrrrrrrrr!