I am a 33 year old girl. Had a thyroidectomy 16 years ago. I've been on synthroid ever since. I've tried Armour, and hated it. I've always felt my best on synthroid. I've been on 150mcg Synthroid for a while, but recently my TSH went up to 4.61. Doctor told me to add in 175mcg 3 times per week. So, I've been doing 150mcg but 175 Mon, Wed, and Fri. It's been 8 weeks and I began having heart palpitations, insomnia, breathlessness, and chest tightness. I got my TSH tested and it was down to .61. Still within "normal" range, but too low for me. I know my body and I have had this condition long enough to know that I don't feel good with a TSH below a 1. I feel my best when my TSH is about 1.5. Any lower than 1 and I experience hyper symptoms, which is exactly what's happening. I did not get my free T3/T4 checked. I skipped one day, and resumed back to just 150mcg. Still experienced hyper symptoms after a few days. So I skipped another dose and then again resumed my 150mcg. It's been 11 days and I still don't feel relief from the hyper symptoms. During these 11 days, I've skipped 2 doses, and haven't taken any 175s, just 150s. How long should these hyper symptoms last?? This is really uncomfortable! I read that the half life of Synthroid is 7-10 days, so I'm guessing that is maybe why I'm still feeling badly? When should I start to feel back to normal? Thank you!