My mom is on medicine for her extremely fast heart rate , it has an average rate of 99 and got up to 165 while she was sleeping. There are many times throughout the day that she can feel her heart beating rapidly in her chest . When I play with my grandma s blood pressure machine my heart rate is never under 90, even when I ve been sitting down for an hour. I can feel my heart in my chest beating rapidly. I also have vasomotor instability disorder, which means I get dizzy a lot from changing positions, for example sitting down to standing up, because gravity naturally pulls everyone s blood down, and my body doesn t push it back up most of the time. Is this just the same problem my mom has? They told her that her heart rate wasn t something to be worried about, it was just scary for her to feel her heart so fast I m 15, and heart problems run in my family. I eat healthy, exercise, and have been a vegetarian for 2 years.