If you feel faint when you stand up or right after exercising, see your doctor. Your doctor will take your blood pressure once while you are lying down and then again as soon as you sit up. A mederma significant drop in systolic pressure the top number in the blood pressure reading is considered a firm diagnosis of orthostatic hypotension. This means you may need to reduce your dose of a diuretic or change to a different drug, Dr. Jacknowitz says. To prevent after-exercise wooziness post exercise hypotension, you’ve got to decrease your heart rate gradually, Dr. McKeag says.