How Low Blood Pressure Is Diagnosed

If you have hypotension (low blood pressure), your healthcare provider will evaluate you using a combination of a physical examination, an investigation of your medical history, and a number of medical tests such as electrocardiogram, blood tests, echocardiogram, stress test, and tilt table test.

These tests often help identify the cause of hypotension, and your doctor will consider your symptoms, medical history, and physical examination when selecting which of these tests you may need.

Labs and Tests

Your healthcare provider may need to perform several tests during an evaluation of hypotension.

Blood Tests

Blood tests to check your blood sugar levels and blood cell count can help identify hypoglycemia (low blood sugar) or anemia (low red blood cells), which are common causes of low blood pressure.

The blood test will simply involve your healthcare provider or the lab technician drawing a sample of your blood, typically from a vein in your arm. Results are usually available within 24 hours.

Valsalva Maneuver

The Valsalva Maneuver is a simple test that requires active participation. It will help your healthcare provider evaluate whether there is a problem with your autonomic nervous system, the part of your nervous system that regulates your heartbeat, and your blood vessel expansion and constriction.

While your blood pressure and heartbeat are being monitored, your healthcare provider will instruct you to take a deep breath and then try to blow out against your mouth while it’s closed, as if you're trying to blow a balloon. You may be asked to do this several times.

Tilt Table Test

Your healthcare provider may order a tilt table test if you have complained of unexplained fainting, one of the symptoms of low blood pressure.

You will be placed on a table that can be adjusted to move you from lying down to an upright position very quickly. Your body’s reaction to being switched between these two positions will be monitored with an electrocardiogram.

Heart Tests

There are several different tests that evaluate your heart that your healthcare provider may order to help in diagnosing the cause of low blood pressure.

Electrocardiogram

This test is used to check for heart problems that may cause your blood pressure to drop. An electrocardiogram (ECG) records the heart's electrical activity, which helps identify structural heart abnormalities, irregularities in heart rhythm, heartbeat speed, and blood supply problems.

The test is non-invasive and involves the attachment of sticky patches (electrodes) to the skin on your chest, arms, and legs. The patches pick up your heart’s electrical signals, while a machine records them and displays them on the screen as a graph.

Echocardiogram

An echocardiogram uses high-frequency sound waves to obtain images of the heart and its chambers. The images show your heart structure, its size, and how well it is pumping.

This test is also non-invasive. You will be connected to an ECG machine with electrodes. The sonographer conducting the test will put a gel substance on your chest and wave a transducer, which is a wand-like object, over the area.

Stress Test

During this test, your healthcare provider will instruct you to exercise. If you’re unable to exercise, you’ll be given medication to make your heart pump faster for the test.

While you are exercising or as the medication takes effect, your heart activity will be measured and recorded by electrocardiogram, nuclear heart scanning, echocardiogram, or positron emission tomography (PET) scan.