The most common symptom is lightheadedness or dizziness when you stand up after sitting or lying down. Symptoms usually last less than a few minutes.

Orthostatic hypotension signs and symptoms include:

• Feeling lightheaded or dizzy after standing up
• Blurry vision
• Weakness
• Fainting (syncope)
• Confusion
• Nausea

When you stand up, gravity causes blood to pool in your legs and abdomen. This decreases blood pressure because there's less blood circulating back to your heart.

Normally, special cells (baroreceptors) near your heart and neck arteries sense this lower blood pressure. The baroreceptors send signals to centers in your brain, which signals your heart to beat faster and pump more blood, which stabilizes blood pressure. These cells also narrow the blood vessels and increase blood pressure.

Orthostatic hypotension occurs when something interrupts the body's natural process of counteracting low blood pressure. Many different conditions can cause orthostatic hypotension, including:

• Dehydration. Fever, vomiting, not drinking enough fluids, severe diarrhea and strenuous exercise with excessive sweating can all lead to dehydration, which decreases 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 prevent your body from responding rapidly enough to pump more blood when standing up.
• Endocrine problems. Thyroid conditions, adrenal insufficiency (Addison's disease) and low blood sugar (hypoglycemia) can cause orthostatic hypotension, as can diabetes — which can 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. Special cells (baroreceptors) near your heart and neck arteries that regulate blood pressure can slow as you age. It also may be harder for an aging heart to beat faster and compensate for drops in blood pressure.
• Medications. 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; certain nervous system disorders, such as Parkinson's disease; and diseases that cause nerve damage (neuropathy), such as diabetes, increase the risk of low blood pressure.
• Heat exposure. Being in a hot environment can cause heavy sweating and possibly 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.

Persistent orthostatic hypotension can cause serious complications, especially in older adults. These 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.