I meant to say generic instead of synthetic -- thanks for the information.
Look at your perscription.
Is it Synthroid, or is it Levothyroxine?
They are both synthetic. Synthroid is a brand name. Levothyroxine is the generic form of the same drug.
You should not accept a generic if your perscription is for Synthroid. The generic contains different inert ingredients, and the strength of the generic is not as uniform as the brand name.