I have been diagnosed with hypothyroidism for over 14 years. I have been on synthroid until 16 months ago and a new dr changed me to naturethroid. At first I had to take both the synthroid and nature throid ( couple months) together because of fluttering of heart at first taking NT. I felt great taking both. Recently I started having palpations after over a year on just NT. Blood levels show normal T3 and T4 but high TSH of 14. I had never had palpations so bad before. They would wake me up at 2-3am these past few weeks. My question is can Some people take both synthroid and naturethroid daily together as a normal medicine regime or do i have to completely change to one or the other. How long will my palpations last if Doctors have increased my dosage...when will they subside??? I just read that NT causes more palpations because of its target on T3.