I'm female, 18, 109lbs, & 5'6". I have recently been told I have sinus tachycardia, I have had an ekg done and a echo. The results for the ekg came back normal just my heart beat was high. And the echo was normal. I was put on a beta blocker, proplanolol. I have been on that for two months, while being on it I have noticed that my heart beat is between 70-89 while laying down. But recently I decided to take it while standing up and yesterday at one point it was 130 while standing. And then I took it later that night after standing for 5 minutes, and it was 90. I took it again today and it was 135. This worries me, is this normal? I know the doctors say my heart is "normal" and they think I will live a long and healthy life, but I think that is a little high for just standing and doing household chores. They think I may be hypothyroid. My tsh level 2 months ago was 4.27. And I recently went back and they said I was more than likely hypo because my levels were up. I go back July 14 for more blood work. But all my other blood work is normal. I also feel like sometimes when I get worked up that my body will shake, so I have to calm down to feel better.