Hi, I'm a newbie here. My 17 then 18 now son was diagnosed in March with an underactive thyroid. He started on 25mg of Levothyroxine. His next blood test in June was normal. He stayed on 25mg and had another blood test a couple of weeks ago and this time his levels were low and he was prescribed 100mg. My son told the doctor that he hadn't been taking it as regularly as he should and had missed a few in the run up to his blood test, but the doctor said don't worry take the 100mg. I feel worried that he should instead stay with his 25mg again as he missed some so surely this would cause his levels to be down and 100mg seems too high a jump. I wondered what you thought and would appreciate any advice. My son is 18 and feels he should just take his doctors advice and won't ask questions and the doctor won't discuss with me direct. Thank you in advance !