Orthostatic Hypotension: Why Do I Have Low Blood Pressure When Standing?

When we stand up, our blood vessels respond to gravity by narrowing. This prevents the blood pressure from falling and ensures a continued oxygen supply to the brain. However, sometimes the blood vessels don't constrict properly, and this causes you to feel lightheaded when standing up. This condition is known as orthostatic hypotension (OH) and is often a symptom of an underlying disorder.

What is orthostatic hypotension?

Orthostatic hypotension  (OH) is a form of low blood pressure that occurs when standing up. The condition is also known as postural hypotension. OH if often mild, with episodes lasting less than a few minutes. The occasional instance of OH is usually for obvious reasons like lack of sleep or dehydration. However, long-lasting OH can be a symptom of a serious condition, and you should immediately see a doctor for further examination.

The normal blood pressure range is between 90/60 and 120/80mm Hg. A reading below 90/60 mm  Hg is considered low blood pressure; but depending on the reason for this, it may not be a cause for concern. Your healthcare provider will likely monitor your blood pressure over a few weeks or months to determine if you have low blood pressure on an ongoing basis.

They will diagnose OH based on individual blood pressure readings and whether your numbers drop by more than 10mmHg in diastolic pressure and 20mmHg in systolic pressure within three minutes of standing. Systolic blood pressure refers to the arterial pressure in the blood vessels when the heart beats, while diastolic blood pressure is the arterial pressure in the blood vessels between the heartbeats while the heart fills with blood.

What happens during orthostatic hypotension?

Adequate blood flow requires a heart strong enough to pump blood and arteries and veins that are capable of expanding and narrowing, as well as enough blood and fluid to flow within the vessels. When you change your body position, several things occur involving the cardiovascular and autonomic nervous systems.

The autonomic nervous system "runs in the background," regulating processes often taken for granted. It consists of the sympathetic and parasympathetic systems. The sympathetic system uses adrenaline to transmit signals to nerve endings, while the parasympathetic system uses acetylcholine.

The parasympathetic nervous system plays a key role in slowing the heart rate, allowing digestion, among other basic metabolic processes.  Acetylcholine is the chief neurotransmitter of the parasympathetic nervous system, which transmits the nerve impulses that enable these processes to occur.  Both of these systems are in balance and need to respond to changes throughout the day.

When you stand, the baroreceptor cells in the aorta and carotid arteries sense the subtle drop in blood pressure due to gravity. The blood flows towards the legs, and the sympathetic system is stimulated almost immediately. As a result, the heart rate increases and causes the heart muscle to contract more forcefully and the blood vessels to constrict.

These actions serve to increase the blood pressure and ensure that an adequate amount of blood reaches the brain and other parts of the body. If the changes don't occur, gravity causes blood to pool in the legs and triggers the symptoms of orthostatic hypotension.

Mild OH is common and can affect anyone, although it's more prevalent in older people and those with pre-existing hypotension (those who normally have low or low to normal blood pressure). Severe cases of OH can cause fainting, blurred vision, and/or confusion.

What are the causes of orthostatic hypotension?

The most common cause of orthostatic hypotension is fluid loss within the blood vessels brought about by dehydration due to diarrhea, vomiting, or medications like diuretics. Diuretics help the body excrete excess water and salt through urination and are commonly used to treat high blood pressure (hypertension) or edema (swelling, such as in the legs).

Underlying conditions

Conditions that cause a drop in the red blood cell count, such as anemia, are also a common cause of OH. Red blood cells are responsible for transporting oxygen throughout the body, and their ability to do their job is compromised when their numbers reduce. As a result, patients can experience dizziness and/or lightheadedness.

Antidepressants

Orthostatic hypotension can be a side effect of certain antidepressants like monoamine oxidase inhibitors (MAOI) and tricyclics.

Alpha-blockers, a class of blood pressure lowering medications,  can also cause OH as they inhibit the vasoconstriction usually initiated by the baroreceptor reflex when you change posture. Examples of this class of drug include doxazosin (Cardura). Alpha-blockers are also sometimes used to treat symptoms of an enlarged prostate.

Beta-blockers, like metoprolol, block the beta-adrenergic receptors and prevent the heart from speeding up and contracting forcefully. As a result, the blood vessels dilate, affecting the body's ability to react to changes.

Erectile dysfunction medications

Cialis, Levitra, and Viagra are medications used to treat erectile dysfunction and dilate the blood vessels, which can trigger OH symptoms of lightheadedness due to low blood pressure. These symptoms can be magnified if these pills are taken together with alcohol, narcotic pain medications, or nitrates (medications used to treat chest pain).

Other medications that can trigger OH symptoms include tetrahydrocannabinol, marijuana, and alcohol.

Medical conditions that cause symptoms related to orthostatic hypotension include:

Pregnancy

Blood volume expands during pregnancy, and this can cause drops in blood pressure, especially with changes in position. This is normal and, barring complications, the blood pressure levels normalize shortly after birth.

Endocrine problems

Hypoglycemia (low blood sugar), Addison's disease (adrenal insufficiency), diabetes, and parathyroid disease can trigger orthostatic hypotension.

Blood loss

Losing a lot of blood from internal bleeding or major injury reduces the amount of blood circulating in the body and causes a sudden drop in blood pressure.

Severe allergic reaction

Common triggers of severe allergies include insect venoms, foods, latex, and certain medications. They can cause hives, swollen throat, breathing problems, itching, and/or a dangerous drop in blood pressure. This condition is called anaphylaxis and usually requires emergency treatment.

Heart problems

Heart attack, heart valve problems, heart failure, and bradycardia are a few of the heart problems that can lead to OH.

Severe infection

Septic shock is a life-threatening drop in blood pressure that occurs when an infection enters the bloodstream.

Lack of nutrients

Insufficient levels of iron, vitamin B12, and folate can keep the body from producing enough red blood cells. The reduced red blood cell count can trigger OH. 

What are the risk factors for orthostatic hypotension?

While orthostatic hypotension can occur in anyone, it's more common in the elderly. This is because atherosclerosis, or hardening of the arteries, which develops with age, makes it difficult for the body to adjust to changes in posture. Additionally, the elderly are more likely to be taking multiple medications that can promote hypotension, and sometimes are prone to dehydration due to decreased thirst sensation.

People who take certain high blood pressure medications are also at an increased risk of developing orthostatic hypotension. In addition, certain conditions like Parkinson's disease and diabetes increase your risk of developing orthostatic hypotension.

Other risk factors for OH include heat exposure, extended bed rest, and alcohol use.

What are the signs and symptoms of orthostatic hypotension?

The symptoms of orthostatic hypotension  include:

• Dizziness

• Blurred vision

• Lightheadedness

• Falling

• Fatigue

• Fainting

• Nausea

• Chest pain

• Neck and shoulder pain

• Leg buckling

The symptoms can go away as the body adjusts to the standing position, or after you sit down for a few minutes. In extreme cases, orthostatic hypotension can cause complications such as falling due to loss of consciousness, which can lead to serious injuries.

Also, the sudden drop in blood pressure reduces blood flow to the brain, thus increasing the risk of stroke. Another complication of orthostatic hypotension is that it masks more severe conditions, including heart failure, heart rhythm problems, and other cardiovascular diseases.

How is orthostatic hypotension diagnosed?

Your doctor will likely look into your medical history if you have been experiencing the above OH symptoms. They will also conduct a series of tests to determine if an underlying condition is causing orthostatic hypotension. If a medication is causing the symptoms, the doctor will try adjusting the dosage or recommend switching to another drug.

Notably, the head-up tilt table test is the standard for determining how one's blood pressure reacts to changes in posture. It involves lying down on a special table that is tilted slightly upward, while strapped down for safety. An IV may be inserted to give medicine.

Also, the doctor may recommend blood tests to determine if you have a low red blood cell count or low blood sugar, both of which can cause low blood pressure. An electrocardiogram (EKG or ECG) monitors the heart's electrical signals during the test and can help uncover heart rhythm irregularities as well as issues with oxygen supply to the heart.

Finally, the doctor may conduct a stress test, which involves monitoring your heart rate and blood pressure while you're exercising.

How is orthostatic hypotension treated?

Restoring normal blood pressure is the main goal of treatment for orthostatic hypotension. This involves helping the blood vessels push blood throughout the body, increasing blood volume, and reducing the pooling of blood in the lower extremities.

Treatment addresses the underlying cause of OH instead of the low blood pressure itself. If you have mild orthostatic hypotension, lying back down immediately after feeling lightheaded usually resolves the symptoms in less than one minute. If the OH is a side effect of medication, reducing the dose, stopping, or changing the medications might make the symptoms disappear.

Other common treatments for orthostatic hypotension include medications, lifestyle changes, and/or use of compression stockings, which are outlined below:

Compression stockings or socks

Compression stockings/socks and abdominal binders can help reduce the pooling of blood in the legs, thus reducing orthostatic hypotension symptoms.

Medication

The most common medications used in the treatment of OH are midodrine and fludrocortisone. These medications are typically prescribed only if non-pharmacologic treatments as listed below are not helpful.

Midodrine is an alpha-adrenergic agonist, which causes blood vessels to constrict, thereby increasing blood pressure, and was the first to be FDA-approved for the treatment of OH. It's not ideal for patients with acute kidney injury or urinary retention. It should be administered at least four hours before bedtime.

Fludrocortisone works by increasing sodium reabsorption from the distal tubules of the kidneys. This expands intravascular blood volume and raises blood pressure. The drug improves supine and standing blood pressure, especially in patients with Parkinson's disease. It works by increasing the amount of fluid in the blood and can have serious side effects. Dosing should be closely monitored by a physician.

Lifestyle changes

Your doctor may suggest multiple lifestyle changes to prevent or manage the symptoms of orthostatic hypotension. These include:

Eat small meals

Your healthcare provider may recommend eating small low-carbohydrate meals if your blood pressure tends to drop after eating.

Get plenty of fluids

Hydration helps prevent symptoms of orthostatic hypotension. Be sure to drink plenty of water before standing for long periods of time or any activities that might trigger OH.

Exercise

Regular strength and cardio workouts can help prevent the symptoms of orthostatic hypotension. Ensure you stretch and flex your muscles before you stand up. Also, exercising in hot and humid weather can trigger OH. If symptoms strike, squeeze your thighs, glutes, and abdominal muscles. Rise onto your tiptoes, squat, or march in place.

Wear waist-high compression stockings

These can improve blood flow while preventing the symptoms of orthostatic hypotension. Only wear compression stockings during the day and take them off before going to bed.

Increase salt in your diet

Be careful with increasing salt in your diet and only do it after consulting with a doctor. Too much salt can lead to high blood pressure, which comes with its own health risks.

Vitamin supplements

Vitamin B12 deficiency and anemia can worsen OH symptoms. As a result, vitamin and iron supplements can be helpful if you are deficient.

Avoid alcohol

Alcohol can trigger or worsen the symptoms of orthostasis so it's best to limit or avoid it altogether.

Don't bend at the waist

Squat by bending your knees when recovering something from the floor.

Get up slowly

You may be able to reduce lightheadedness and dizziness that comes with orthostatic hypotension by standing up slowly.

Raise your head in bed

Sleeping with your head slightly raised on a pillow can alleviate orthostatic hypotension when you get up in the morning.

Orthostatic hypotension in children

Even though orthostatic hypotension is more common in the elderly, it also occurs in older children and can be related to the future development of hypertension. It mainly manifests with symptoms like syncope and dizziness.

Syncope is a brief loss of consciousness that can occur when the brain doesn't get enough blood and oxygen. In children, syncope can be life-threatening as it often indicates underlying cardiac or neurological problems.

Other symptoms of orthostatic hypotension in children include lightheadedness, changes in vision, nausea, and/or cold, damp skin.

Obesity and excess weight are recognized as risk factors for orthostatic hypotension. Other causes of OH in children include:

• Anaphylaxis – life-threatening allergic reactions

• Certain medications like painkillers and anti-anxiety drugs

• Drinking alcohol (teenagers)

• Infection

• Changing positions suddenly and standing quickly

• Arrhythmia (abnormal heart rhythm)

• Dehydration

• Heart conditions

Treatment of pediatric OH can include non-drug therapy and the same lifestyle changes recommended for adults but requires a physician to investigate for an underlying cause and treat it accordingly.

Orthostatic hypotension during pregnancy

Orthostatic hypotension or any other form of low blood pressure during pregnancy is common but should be monitored closely by a physician.

Big drops in blood pressure can be a symptom of a serious or even life-threatening condition. It can lead to shock, falls, and/or organ damage. It may also be a symptom of ectopic pregnancy, which occurs when a fertilized egg implants abnormally outside the uterus.

While there is some research into the effects of orthostatic hypotension on a fetus, the data is limited. However, studies suggest that low blood pressure during pregnancy can lead to complications like low birth weight and stillbirths¹.

Orthostatic hypotension in pregnant women exhibits the same symptoms as noted above. Additional symptoms may include rapid or shallow breathing, lack of concentration, unusual thirst, and tiredness.

Call your healthcare provider if you experience any symptoms of OH during pregnancy. 

Is orthostatic hypotension life-threatening?

Although orthostatic hypotension usually resolves quickly and is rarely harmful, it can be life-threatening in severe cases. It should be taken seriously because orthostatic hypotension increases the risk of developing cardiovascular problems.

Researchers at the University of North Carolina found that people with orthostatic hypotension are 54% more likely to suffer heart failure² than those without OH. They also found that OH appears to be related to conditions that can cause diabetes and coronary heart disease. This can make orthostatic hypotension life-threatening.

When should you see a doctor for orthostatic hypotension?

A person with low blood pressure issues should be aware of the symptoms of orthostatic hypotension. They should also know what medications may be causing a drop in blood pressure when they start taking them.

That said, occasional dizziness and lightheadedness due to OH may be minor. It may be triggered by low blood sugar, mild dehydration, overheating, or sitting down for a long time.

Whatever the cause, there is no reason for concern if the OH symptoms only happen occasionally, are minor, and resolve quickly.

It's crucial that you see a doctor immediately if you experience orthostatic hypotension symptoms frequently. It is particularly important that you do so if you lose consciousness, even if it's just for a few seconds.

Record your symptoms after they occur, indicating when they occurred, how long they lasted, and what you were doing at the time of onset.

The lowdown

Orthostatic hypotension can be unsettling and even dangerous if you lose consciousness, fall, or pass out. The symptoms usually improve and eventually resolve shortly after you sit or lie down.

Talk to your doctor and be honest about your symptoms and any medications you are taking. Don't forget to adopt the recommended lifestyle changes – increase salt intake (as monitored by your doctor to ensure that you do not ingest too much), stand up slowly, eat small meals, and drink plenty of fluids.