I stopped taking 10 mcg T3 with my T4 as I developed atrial fibrillation. But on 100 mcg T4 only I felt not 100%, and my free T3 was low. I have tried reintroducing T3 with a lower dose of T4, but feel that it is now causing heart palpitations. I went from 10 to 5 mcg of T3 in 2 doses but still feel not quite right. Thought I would try the Ken Blanchard approach and take 2.5 mcg T3 with 90 of T4. But should I still split the dose of T3? I have 5 mcg tablets and can split them into two with a pill cutter, but they shatter when trying to split them further. ( I have not yet read his book so don't know what he suggests).