How to diagnose Hypotension ? 
 Hypotension is diagnosed based on your medical history, a physical exam, and test results. Your doctor will want to know:
                
The type of hypotension you have and how severe it is
                
Whether an underlying condition is causing the hypotension
                
Specialists Involved
                
A primary care doctor or specialist may diagnose and treat hypotension. The type of specialist most commonly involved is a cardiologist (heart specialist).
                
Other specialists also may be involved, such as surgeons, nephrologists (kidney specialists), or neurologists (brain and nerve specialists).
                
Diagnostic Tests
                
Shock is a life-threatening condition that requires emergency treatment. For other types of hypotension, your doctor may recommend tests to find out how your blood pressure responds in certain situations.
                
The test results will help your doctor understand why you're fainting or having other symptoms.
                
Blood Tests
                
During a blood test, a small amount of blood is taken from your body. It's usually drawn from a vein in your arm using a needle. The procedure is quick and easy, although it may cause some short-term discomfort.
                
Blood tests can show whether anemia or low blood sugar is causing your hypotension.
                
EKG (Electrocardiogram)
                
An EKG is a simple test that detects and records your heart's electrical activity. It shows how fast your heart is beating and whether its rhythm is steady or irregular. An EKG also shows the strength and timing of electrical signals as they pass through each part of your heart.
                
Holter and Event Monitors
                
Holter and event monitors are medical devices that record your heart's electrical activity. These monitors are similar to an EKG. However, a standard EKG only records your heartbeat for a few seconds. It won't detect heart rhythm problems that don't occur during the test.
                
Holter and event monitors are small, portable devices. You can wear one while you do your normal daily activities. This allows the monitor to record your heart for longer periods than a standard EKG.
                
Echocardiography
                
Echocardiography (echo) is a test that uses sound waves to create a moving picture of your heart. The picture shows how well your heart is working and its size and shape.
                
There are several types of echo, including stress echo. This test is done as part of a stress test (see below). Stress echo usually is done to find out whether you have decreased blood flow to your heart, a sign of coronary heart disease (also called coronary artery disease).
                
Stress Test
                
Some heart problems are easier to diagnose when your heart is working hard and beating fast. During stress testing, you exercise (or are given medicine if you're unable to exercise) to make your heart work hard and beat fast while heart tests are done.
                
These tests may include nuclear heart scanning, echo, and positron emission tomography (PET) scanning of the heart.
                
Valsalva Maneuver
                
This is a simple test for the part of your nervous system that controls functions such as your heartbeat and the narrowing and widening of your blood vessels. If something goes wrong with this part of the nervous system, blood pressure problems may occur.
                
During this test, you take a deep breath and then force the air out through your lips. You will do this several times. Your heart rate and blood pressure will be checked during the test.
                
Tilt Table Test
                
This test is used if you have fainting spells for no known reason. For the test, you lie on a table that moves from a lying down to an upright position. Your doctor checks your reaction to the change in position.
                
Doctors use a tilt table test to diagnose orthostatic hypotension and neurally mediated hypotension (NMH). People who have NMH usually faint during this test. The test can help your doctor find any underlying brain or nerve condition.