Hi my names ann, I thought I would write because most people don't get on with there medicine. I was diagnosed with under active thyroid 5 months ago, when just going for a general mot. I am 72, but very active I would say still working, walking, swimming. I hadn't noticed being tired or anything. I was given 50 levithyroxine. I must say after a few days I felt brighter, hadn't noticed anything wrong before. After 3 months had another test, and was given 100. But I had noticed before hand I was a bit tetchy, so I wasn't surprised. It seems my thyroid had just packed in. Great on melds, and I have lost 7lb, so all good.