The most common symptom of orthostatic hypotension is feeling lightheaded or dizzy when you stand up after sitting or lying down. This feeling, and other symptoms, usually happens shortly after standing up and generally lasts only a few seconds. Orthostatic hypotension signs and symptoms include:
- Feeling lightheaded or dizzy after standing up
- Blurry vision
- Fainting (syncope)
When to see a doctor
Occasional dizziness or lightheadedness may be relatively minor — the result of mild dehydration, low blood sugar, or too much time in the sun or a hot tub, for example. Dizziness or lightheadedness may also happen when you stand after sitting for a long time, such as in a lecture, concert or church. If these symptoms happen only occasionally, it's usually not cause for concern.
It's important to see your doctor if you experience frequent symptoms of orthostatic hypotension because they sometimes can point to more-serious problems. It can be helpful to keep a record of your symptoms, when they occurred, how long they lasted and what you were doing at the time. If these occur at times that may endanger you or others, discuss this with your doctor.
When you stand up, gravity causes blood to pool in your legs. This decreases blood pressure because there's less blood circulating back to your heart to pump.
Normally, special cells (baroreceptors) near your heart and neck arteries sense this lower blood pressure and send signals to centers in your brain that in turn signal your heart to beat faster and pump more blood, which stabilizes blood pressure. In addition, these cells cause blood vessels to narrow, which increases resistance to blood flow and increases blood pressure.
Orthostatic or postural hypotension occurs when something interrupts the body's natural process of counteracting low blood pressure. Orthostatic hypotension can be caused by many different conditions, including:
- Dehydration. Fever, vomiting, not drinking enough fluids, severe diarrhea and strenuous exercise with excessive sweating can all lead to dehydration. When you become dehydrated, your body loses blood volume. Mild dehydration can cause symptoms of orthostatic hypotension, such as weakness, dizziness and fatigue.
- Heart problems. Some heart conditions that can lead to low blood pressure include extremely low heart rate (bradycardia), heart valve problems, heart attack and heart failure. These conditions may cause orthostatic hypotension because they prevent your body from being able to respond rapidly enough to pump more blood when needed, such as when standing up.
- Endocrine problems. Thyroid conditions, adrenal insufficiency (Addison's disease), low blood sugar (hypoglycemia) and, in some cases, diabetes can trigger low blood pressure. Diabetes can also damage the nerves that help send signals regulating blood pressure.
- Nervous system disorders. Some nervous system disorders, such as Parkinson's disease, multiple system atrophy, Lewy body dementia, pure autonomic failure and amyloidosis, can disrupt your body's normal blood pressure regulation system.
- After eating meals. Some people experience low blood pressure after eating meals (postprandial hypotension). This condition is more common in older adults.
The risk factors for orthostatic hypotension include:
- Age. Orthostatic hypotension is common in those who are age 65 and older. As your body ages, the ability of special cells (baroreceptors) near your heart and neck arteries to regulate blood pressure can be slowed. Also, when you age, it may be harder for your heart to beat faster and compensate for drops in blood pressure.
Medications. People who take certain medications have a greater risk of orthostatic hypotension. These include medications used to treat high blood pressure or heart disease, such as diuretics, alpha blockers, beta blockers, calcium channel blockers, angiotensin-converting enzyme (ACE) inhibitors and nitrates.
Other medications that may increase your risk of orthostatic hypotension include medications used to treat Parkinson's disease, certain antidepressants, certain antipsychotics, muscle relaxants, medications to treat erectile dysfunction and narcotics.
Using medications that treat high blood pressure in combination with other prescription and over-the-counter medications may cause low blood pressure.
- Certain diseases. Some heart conditions, such as heart valve problems, heart attack and heart failure, and certain nervous system disorders, such as Parkinson's disease, put you at a greater risk of developing low blood pressure.
- Heat exposure. Being in a hot environment can cause you to sweat and, possibly, cause dehydration, which can lower your blood pressure and trigger orthostatic hypotension.
- Bed rest. If you have to stay in bed a long time because of an illness, you may become weak. When you try to stand up, you may experience orthostatic hypotension.
- Pregnancy. Because your circulatory system expands rapidly during pregnancy, blood pressure is likely to drop. This is normal, and blood pressure usually returns to your pre-pregnancy level after you've given birth.
- Alcohol. Drinking alcohol can increase your risk of orthostatic hypotension.
While mild forms of orthostatic hypotension may be a nuisance, more-serious complications are possible, especially in older adults. These complications include:
- Falls. Falling down as a result of fainting (syncope) is a common complication in people with orthostatic hypotension.
- Stroke. The swings in blood pressure when you stand and sit as a result of orthostatic hypotension can be a risk factor for stroke due to the reduced blood supply to the brain.
- Cardiovascular diseases. Orthostatic hypotension can be a risk factor for cardiovascular diseases and complications, such as chest pain, heart failure or heart rhythm problems.