Sorry this is longwinded - I hope you can bear with me! I've got Hashi's and had all the hypo symptoms for over 16 years despite thyroxine replacement and "normal" blood tests; then changed to Armour (a bit better) but no big improvement. Dr P suggested adrenal supplement after saliva tests revealed low cortisol etc. He later suggested a trial of T3 only, which I kept putting off. Decided to go for it in Jan, reduced Armour right down then stopped it and slowly introduced the T3. I kept waiting for Paul R's "lightbulb" moment which never came. I got to 55 mcg per day, and had a function test that read TSH 2.0, T4<5, T3 3.8. So I carried on upwards to 75mcg, with no improvement in energy till an enlightened endo from Leamington Spa suggested I might be iron deficient and to get tests. Sure enough serum iron, ferritin and transferrin saturation were all low. Last week I began a liquid supplement from the health shop (10ml, twice daily). A couple of days later I had slight palpitations in the afternoon. I reduced one of the divided T3 doses and all was ok for a few days. But two days ago I suddenly got massive palpitations and irregular heartbeat, again in the afternoon. It went on for hours and all night, easing off at about 8 am yesterday morning. I cut the T3 down to 35mcg yesterday and took no iron at all. Today I took just 1 tsp iron and slightly increasing T3 again. This all seems so ad hoc and hit and miss, and with regular function tests being of less use when on T3 only, I just don't know what to do. (Newish) GP reluctantly prescribes T3 (after receiving endo's recommendation) but is not much interested in my story, nor seems to know much about T3 only regimes. I'm seeing him next week, anxious that he might tell me to forget the whole experiment. (Although if I thought thyroid medication uptake is being scuppered by lack of iron rather than T4 conversion problems I might even be relieved to go back to Armour and take the pills just once a day) What are other people's experiences of taking T3 only? Has anyone else on thyroid medication had trouble introducing iron? What is the best type of iron? I'm desperate to get my thyroid managed better, not just to relieve all the symptoms everyone on this forum knows about, but also because I have increasing deafness, tinnitus, pressure in ears and bouts of dizziness which I've read can be connected with poor thyroid function and low iron. Any comments or suggestions would be much appreciated, thanks.