@learningstudent, I moved you recent question to this discussion that you started a couple of days ago. I did this as your questions appear to be related and give members more information to share their experiences.
This excerpt states:
"A person’s heart rate is usually about 70 to 80 beats per minute when resting. Normally, the heart rate increases by 10 to 15 beats per minute when standing up, and then it settles down again. For people with postural tachycardia syndrome, the heart rate goes up considerably higher when they stand, often increasing 30 to 50 beats per minute or more. This can lead to lightheadedness, dizziness and fainting."