I have hypothyroid and have been on T4 for 27-28 years when it failed me, terrible headaches, brain fog & palipatations when I finally, after 90 days of waiting, got an appt. with an endo, who immediately put me on 75 mcg, down from 88mcg, of T4, and 5mcg of T3. It immediately made me feel better than T4 alone. The T4 was Synthroid, a synthetic drug that cost me a buck a pill and the T3 was a generic "free" pill. I realized that the generic drug Levothyroxine had been changed from Synthroid, by the Pharmacists, years ago, but couldn't remember how many years, and the T4 was generic so I decided, after palipatations every morning at the same time to change the Synthroid but when I called the endo, his assistant, secretary, informs me that I can't even see the endo until I see a heart doctor for the palipatations, she says I have to notify my primary, so I do, and he sees me the same day. As soon as I tell him I just want to see the endo about switching the T4 to generic to not pay for it and that it gave me heart palipatations he says he'll write the switch but then when I mention I'm on generic T3 he lectures me, tells me T3 is useless and says he can prove it. I ask him how and he says if I take a blood test it will show that I have an excess of T3 in my body now because it does not "work," and he will switch me back to T4 only Levothyroxine and gives me a prescription for the blood test: Serrum B12, TSH, Free T4 & Free T3. And, I am really sweating it because maybe he "knows" something I don't but after only 3 weeks on only 5 mcg of T3 how could that happen? Anyone have a similar experience or have any idea about T3 being too high and "not working" as my primary said? Thanks.