My doctor told me last week i have an under active thyroid and i need to take medicine for it? what kind of meds do i need?

Levothyroxine: The best form of thyroid replacement is levothyroxine. A common "brand" is synthroid, but there are a number of generics. They are all fairly inexpensive. Once you get started on one of these, try to stick with the same brand and take it at the same time of day. Your doctor may need to make some dose adjustments after your initial starting dose.