Here levothyroxine is the generic of synthroid. Sythroid is the original brand name. They claim there's no difference but I've always found the quality of 'synthroid' as well as my response to it to be better. The doctor should maybe start you off in lower dosages. I couldn't sleep at first when they started me on thyroid replacement over 20 years ago even though I was dangerously low by then. The doctor slapped a full dose on me (100 mg) when now it's done in small increments beginning with a low dose and testing the blood. Everyone is different. I've tried the t3 and it gave me bad side affects -- one of them being nervousness. I didn't like it. My goal now is to be on a low of a dose as possible with the most maximum benefit. It has to be adjusted for me a lot. In other words, I either goes too high or too low.