I took 150 mcg's of thyroxine for 30yrs, was told to cut back to 125 mcg's of thyroxine three months ago. Was tested on 125 mcg's last week and told to cut back to 100 mcg's of thyroxine. In the last year I have taken Simvastatin tablets and 100 mg of CoEnzyme Q10. I never thgought it possible to come down to 100 mcg's after taking 150 mcg's for thirty years. No idea what my readings are as I never ask , I take the doctors word for it and assume they know what they are doing. Has this happened to any one else ? Any advice would be helpful.