It can be caused by not getting enough fluids, blood loss, some medical conditions, or medications, including those prescribed for high blood pressure. If you have low blood pressure, you may feel lightheaded, weak, dizzy, or even faint. Low blood pressure, or hypotension, is systolic blood pressure lower than 90 or diastolic blood pressure lower than 60.Blood pressure levels are classified based on those two numbers. The second number, called diastolic blood pressure, is the pressure when your heart relaxes and fills with blood.Ī blood pressure reading is given as the systolic blood pressure number over the diastolic blood pressure number. The first number, called systolic blood pressure, is the pressure caused by your heart contracting and pushing out blood. When a health care professional measures your blood pressure, they use a blood pressure cuff around your arm that tightens and then gradually loosens. Blood pressure is the force of blood pushing against the walls of arteries as the heart pumps blood.
