I too take synthroid. How long were you on it before you had blood work or something else done to prove it wasn't working? What dose were you on? I was HYPO feeling for years but my blood work always read normal so my GP at the time didn't bother with meds(wish she would have tried). Last year I found a lump in my neck and had 2 surguries to have the thyriod removed due to 2 kinds of cancer. I was made to stay severly hypo for 4 months before I had radiation treatment and started on meds. I know for a fact that it takes AT LEAST 6 weeks before the thyroid levels balance out when you take meds, this includes each time you increase or derease the dose. Just curious to know your experience!