My free t4 is 1.5 and t3 is 2.7 and tsh 2.29 while currently on syn. 50mcg. having fast heart rate and insomnia. endo wants to add cytomel (liothyronine). good?

Depends: It depends on the doctor. My opinion would be to try a different type of levothyroxine first. If you are on generic, you could go to brand synthroid or tirosint. People absorb these metabolic medicines differently, and a different type might normalize your T3 (liothyronine) (which is pretty close anyway).

No: Hi. I can't imagine why an ENDO of all people would want to add Cytomel (liothyronine) based on those labs (and that MUST be a FREE T3, not a total T3). Adding T3 (Cytomel (liothyronine)) will most likely NOT help your fast heart rate and insomnia, and those labs look fine! Good luck!