I used to have pretty high FT4 (18+) and relatively low normal FT3 (4.7) and felt rubbish.
Last year, on T3 only, I had mid range FT4 and still low normal FT3 (3.9 - in 3.1 - 6.8). Increased T3 a little (just a quarter of a tablet) and now I have under range FT4, just about same FT3 as I had when I started (4.7 in 3.1-6.8) and, of course, under range TSH. But I do feel better than before - but still run out of steam quite often and need to sleep for 12 hours +.
Do I increase T3 a bit more? Give up and just sleep a lot, as It doesn't look as though I'll ever get FT3 up, or what? I'm sure Diogenes could tell me whether I am a good or poor converter or whatever, but I'm stuck.
Tests all at pretty much the same time of day, fasting, with 12+ hours since last T3 dose.