Diagnosis

The goal in testing for low blood pressure is to find the underlying cause. Besides taking your medical history, doing a physical exam and measuring your blood pressure, your doctor might recommend the following:

  • Blood tests. These can provide information about your overall health as well as whether you have low blood sugar (hypoglycemia), high blood sugar (hyperglycemia or diabetes) or a low red blood cell count (anemia), all of which can cause lower than normal blood pressure.
  • Electrocardiogram (ECG). During this painless, noninvasive test, soft, sticky patches (electrodes) are attached to the skin of your chest, arms and legs. The patches detect your heart's electrical signals while a machine records them on graph paper or displays them on a screen.

    An ECG, which can be performed in your doctor's office, detects irregularities in your heart rhythm, structural abnormalities in your heart, and problems with the supply of blood and oxygen to your heart muscle. It can also tell if you're having a heart attack or have had one in the past.

    Heart rhythm abnormalities come and go, and an ECG might not find them. You might be asked to wear a 24-hour Holter monitor to record your heart's electrical activity as you go about your daily routine.

  • Echocardiogram. This noninvasive exam, which includes an ultrasound of your chest, shows detailed images of your heart's structure and function.

    Ultrasound waves are transmitted, and their echoes are recorded with a device called a transducer, which is held outside your body. A computer uses the information from the transducer to create moving images on a video monitor.

  • Stress test. Some heart problems that can cause low blood pressure are easier to diagnose when your heart is working harder than when it's at rest. During a stress test, you'll walk on a treadmill or do some other form of exercise. You might be given medication to make your heart work harder if you're unable to exercise.

    When your heart is working harder, your heart will be monitored with electrocardiography or echocardiography. Your blood pressure also may be monitored.

  • Valsalva maneuver. This noninvasive test checks the functioning of your autonomic nervous system by analyzing your heart rate and blood pressure after several cycles of a type of deep breathing: You take a deep breath and then force the air out through your lips, as if you're trying to inflate a balloon.
  • Tilt table test. If you have low blood pressure on standing, or from faulty brain signals (neurally mediated hypotension), a tilt table test can evaluate how your body reacts to changes in position.

    During the test, you lie on a table that's tilted to raise the upper part of your body, which simulates the movement from horizontal to a standing position.