Is it normal for a 19 year olds s heart rate to increase when i sit up and it goes back to normal when i lay down? in the er yesterday it was 138 when i sat up but 70-90 when i layed they monitored me when i layed down the whole time then let me go

Not normal.: A resting heart rate in a sitting or standing position should be below 90 in healthy young male, although it may rise transiently if going from lying down to standing and then should stabilize. Dehydration, fever, anxiety, anemia, overactive thyroid can all cause an increase in heart rate, so if persistent rapid pulse, discuss with your doctor.