Would it hurt a person to take 40mgs of midodrine at 1 time?

Potentially. This stuff is used to raise blood pressure, especially in folks with orthostatic hypotension ( BP drops when they stand up) the normal dose is 10 mg 3 times a day.....So i would be afraid of trying 40 mg at once. Most folks start slowly, and do not even take 10mg at a time...Some suggest starting with 2.5 mg....So i say no to 40mg!