I have had an underachieve thyroid for the past 11 years and have been on 100mcg of Thyroxine for a good number of years. Three times now I have gone for my regular blood test and it has shown I am taking too much thyroxine and my dose has been reduced to 75mcg and within a week I hit the deck running feeling dreadful! They put me back up to 100 and my next blood test is fine!!! GP has reduced it again saying its dangerous to have too much to 75 and now I feel horrific! My last blood test showed Free T4 21.2 TSH 0.08 .....just taken myself to docs for a repeat to see how the reduced thyroxine has effected me. A few years ago I had a scan and it showed I have nodules on my thyroid. Was assured it was nothing to worry about...can these nodules produce hormones and that be the reason I am showing over medicated. Thanks for reading this ....off for a lie down!