Overview of Hypotension

We hear a lot about high blood pressure (hypertension) and what can happen if it isn't controlled, but having abnormally low blood pressure (hypotension) can be just as harmful if it not properly treated.

Unlike high blood pressure symptoms, which are poorly defined and often totally absent, low blood pressure symptoms tend to be more upfront and easily recognizable. The development of symptoms is often a warning sign of a potentially serious underlying disorder. Generally speaking, your blood pressure would need to fall pretty dramatically before symptoms develop.

Symptoms

Symptoms of low blood pressure can vary based on how quickly and/or steeply your blood pressure drops. If it develops quickly, you may end up passing out (fainting). By contrast, if it develops gradually, you may feel tired and weak but be otherwise unaware of your condition.

Symptoms of low blood pressure may include:

• Dizziness 
• Lightheadedness
• Blurry vision
• Fatigue
• Weakness
• Lack of concentration
• Heart palpitations
• Nausea
• Syncope (fainting or passing out)

Complications

Low blood pressure is usually most serious when it reduces the blood flow to critical organs, such as your heart or lungs, and this reduced blood flow continues for a long time. Within minutes, a reduced blood supply to the heart or brain can result in irreversible damage. Chronically low (or even borderline low) blood pressure can have an adverse effect on the kidneys as well.

If the drop is sudden and severe, people will often describe a feeling of "impending doom." In rare instances, a dramatic drop can lead to syncope (fainting), shock, coma, and even death.

Even a relatively mild drop in blood pressure while standing (referred to as orthostatic hypotension) can be dangerous if you lose consciousness and fall.

Causes

While there are a number of things that can cause a steep drop in blood pressure, one of the most common is taking too high a dose of antihypertensive medication.

Other causes are related directly or indirectly to conditions that affect either the blood volume (how much blood circulates in the vessel) or the rate of circulation (how strongly the blood moves through the vessels).

When investigating the cause of your low blood pressure, your healthcare provider may look into the following possible causes:

• Overuse of blood pressure medications
• Depressant medication, including opioids and anesthetics
• Dehydration
• Heart failure
• Heart arrhythmias
• Diabetes
• Bleeding, internal or external
• Thyroid problems
• Addison's disease (adrenal insufficiency)
• Anaphylaxis (a potentially life-threatening allergy)
• Peripheral vascular disease
• Neurogenic mediated hypotension

Increasing heart rate sends more blood through the blood vessels over time than if the heart was beating more slowly.

Over time, this compensation would have its ill effects. Depriving the arms and legs of blood can lead to muscle atrophy and wasting. Blood flow to the intestines may also be diverted, which can result in tissue damage and severe gastrointestinal bleeding.

Moreover, a sustained heart rate over 100 beats per minute can eventually compromise the heart muscle itself, increasing the risk of heart failure and sudden death.

Diagnosis

Hypotension can be diagnosed by using a blood pressure cuff. The cuff measures both the systolic pressure (the pressure exerted in your blood vessels when your heart beats) and the diastolic pressure (the pressure in your blood vessels when your heart rests between beats).

The reading is described by the systolic pressure over the diastolic pressure, such as 120/80 (the borderline normal reading for adults in the United States).

While hypotension doesn't have an exact definition, many healthcare providers consider 90/60 to be the cut-off point by which hypotension can be reasonably diagnosed. Unfortunately, this doesn't fully represent what low blood pressure really means.

For example, athletes in excellent physical shape may have a blood pressure of 85/50 and not be considered hypotensive. On the other hand, a person with coronary artery disease may be considered hypotensive with a blood pressure reading of 120/70.

Without adequate blood flow, the tissues of the body will be deprived of oxygen and nutrients needed to function normally. An inadequate supply of oxygen to the tissues — referred to as tissue hypoxia — can eventually lead to cell death.

Other Tests

To pinpoint the underlying cause, your healthcare provider may order blood tests to check if you have diabetes, anemia, or conditions associated with hypotension.

An electrocardiogram (ECG) can be used to detect heartbeat irregularities, structural heart abnormalities, and problems with the supply of blood and oxygen to the heart muscle. Similarly, a type of ultrasound known as an echocardiogram can provide detailed images of your heart's structure and function.

A stress test, performed on a treadmill or stationary bike, can evaluate your heart during activity with either an ECG or echocardiogram. A tilt table test can be used to assess changes in blood pressure at different angles and is useful in diagnosing orthostatic hypotension and neurogenic mediated hypotension.

Treatment

The treatment of hypotension is dependent on the underlying causes. It is not uncommon for people prescribed high blood pressure medications to end up with blood pressure that is too low. A simple dose adjustment is all that may be needed to correct the condition.

If dehydration contributes to the problem, increased fluid intake would be needed based in part on your body mass index (BMI). For example, a person with a normal BMI would likely only need eight to 10 8-ounce glasses of water per day to maintain ideal hydration. People with a high BMI may need far more. Adding more salt to your diet may also aid in normalizing your blood pressure.

Compression socks may also help by forcing pooling blood in the legs back toward the core. This is a common treatment for people with heart failure and other circulatory disorders.

In some case, medication may be prescribed to counteract physiological abnormalities that other interventions can't. These include Florinef (fludrocortisone), which boosts your blood volume, and Orvaten (midodrine) which restricts blood vessels and raises the blood pressure.

A Word From Verywell

Low blood pressure can cause serious problems if left undiagnosed or untreated. Even if the symptoms seem "manageable," don't ignore them or try to live with them. See your healthcare provider or ask for a referral to a cardiologist for further evaluation. Treatment is available.