It is easy to fill out a yellow card alert online about medication. An endo I saw yesterday was really suprised when I told her I gained weight on T4 thyroxine. Weight gain seems to be a little know side effect amongst medics and I wonder if they would be a bit keener to prescribe T3 if they knew what a common side effect weight gain is on T4. So I am suggesting that everyone from this forum who has experianced weight gain on t4 only medication fill out a yellow card alert for thyroxine and alert weight gain as a side effect. You just need to google yellow card to find website to do this and all the alerts are published.