Heart & Circulatory Health

Low Blood Pressure (Hypotension)

Written by
Dr. Sneha Kannan
and medically reviewed by Dr. Amiya Kumar Chattopadhyay

Published on May 07, 2019 and last reviewed on Oct 14, 2019   -  5 min read



Blood pressure is the force exerted by the blood flowing in the blood vessels on the walls of the vessels. Without this force, oxygen and nutrients would not reach the tissues and organs of the body. The heart exerts this pressure by forcing the blood out with every contraction. The increase or decrease of blood pressure depends on the circumference of the blood vessel and the force by which the heart pumps the blood

Low Blood Pressure (Hypotension)

What Is Blood Pressure?

Blood pressure is the force exerted by the blood flowing in the blood vessels on the walls of the vessels. Without this force, oxygen and nutrients would not reach the tissues and organs of the body. The heart exerts this pressure by forcing the blood out with every contraction. The increase or decrease of blood pressure depends on the circumference of the blood vessel and the force by which the heart pumps the blood.

The normal blood pressure is 120/80 mmHg, which is measured using a sphygmomanometer. The reading consists of two figures:

  1. Systolic pressure - It is the higher value, which indicates the contractions of the heart.

  2. Diastolic pressure - It is the lower value and indicates the resting period between heartbeats.

The blood pressure can vary by up to 30 to 40 mmHg during a day. Blood pressure is high during exercise, stress, and anxiety, and the lowest while sleeping.

What Is Hypotension?

Hypotension is the medical term used to describe blood pressure less than 90/60 mmHg. Slight fall in the blood pressure causes no problem in healthy individuals. But abnormally low pressure can cause fainting and dizziness, and can also be fatal.

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What Are the Symptoms of Low Blood Pressure?

When the pressure falls suddenly, you might have signs and symptoms like:

What Are the Types of Hypotension?

The different types of hypotension are:

  1. Orthostatic or Postural Hypotension - Orthostatic or postural hypotension is caused due to a sudden drop in the pressure, which results from a change in posture, for example, getting up after sitting or lying. The pressure returns to normal quickly.

  2. Postprandial Hypotension - In older people with diabetes and high blood pressure, the blood pressure drops after eating. For digestion, the intestines need more blood, so the heart beats faster to pump more blood and other blood vessels become narrow to maintain the blood pressure. As a person ages, this process becomes less effective.

  3. Neurally Mediated Hypotension - On standing, the blood gets collected in the legs, and the heart adjusts to maintain normal pressure. But in neurally mediated hypotension, due to problems in signals sent between the heart and the brain, the heart rate and blood pressure drop.

  4. Multiple System Atrophy with Orthostatic Hypotension - Here, low blood pressure results due to continuous damage to the autonomic nervous system, which controls the blood pressure. This condition is also called Shy-Drager syndrome.

What Causes Low Blood Pressure?

Many factors can cause hypotension. Some of the common reasons are:

  • Heart Problems - In heart conditions like bradycardia (low heart rate), heart attack, heart failure, and heart valve problems, the blood pressure becomes low as the heart cannot pump enough blood.

  • Medications - Some medicines like alpha blockers, beta blockers, and diuretics are used to lower high blood pressure. Other medicines that can lower the blood pressure are tricyclic antidepressants, Parkinson’s disease drugs, and Sildenafil (Viagra).

  • Hormonal Imbalance - Any problem in the thyroid or the adrenal gland can cause hormonal imbalance and can lower the blood pressure. The thyroid gland controls the heart rate and blood pressure, and the adrenal gland is responsible for stress response.

  • Eating Disorders - People with anorexia nervosa and bulimia have abnormally slow heart rate and irregular heartbeats, which can lead to serious hypotension and heart failure.

  • Pregnancy - As the circulatory system expands during pregnancy, the systolic pressure falls 5 to 10 points, and the diastolic pressure falls 10 to 15 points.

  • Surgery - Intentionally lowering the blood pressure during surgery results in less blood loss.

  • Dehydration - When you lose more water and nutrients than you consume, it can cause dizziness and weakness.

  • Septicemia - Septicemia is when an infection enters the bloodstream. This results in a drastic drop in the blood pressure called septic shock, which can be fatal.

  • Anaphylaxis - Anaphylaxis is a severe allergic reaction which can be triggered by food, medicines, and insect bites. It causes hives, breathing problems, drop in blood pressure, and swollen throat.

  • Nutritional Deficiency - Vitamin B12 and folate deficiency can cause anemia, which can lead to hypotension.

  • Other Causes - Actions like swallowing, coughing, urinating, and emptying your bowel can stimulate the vagus nerve, which raises acetylcholine levels in the body. Acetylcholine reduces blood pressure by dilating the blood vessels.

When Is Low Blood Pressure an Emergency?

Severe hypotension can result in shock, which can be life-threatening. The signs and symptoms of shock are:

  • Confusion.

  • Cold and clammy skin.

  • Weak and rapid pulse.

  • Shallow and rapid breathing.

Seek immediate medical attention if you notice any of these symptoms.

What Are the Risk Factors for Hypotension?

Some types of hypotension depend on the following factors:

  • Age - Postural hypotension is common in people older than 65 years, and the neurally mediated type is usually seen in children and young adults.

  • Certain Health Conditions - Conditions like diabetes, Parkinson’s disease, and heart problems increase the risk of low blood pressure.

  • Medicines - As already mentioned, taking certain drugs can lower blood pressure.

How Is Hypotension Diagnosed?

Most doctors consider the blood pressure to be low only if it causes symptoms. Apart from checking your blood pressure, the doctor might order the following tests to know the cause of hypotension.

  • Blood Test - To check if you have anemia or diabetes or hypoglycemia (low blood sugar).

  • ECG, Echocardiogram, and Stress Test - These tests are done to detect irregularities in heart rhythm, problems with the blood and oxygen supply to the heart, and structural abnormalities of the heart.

  • Tilt Table Test - Here, you lie on a table that is tilted and the upper part of your body is raised to simulate orthostatic hypotension.

How to Treat Hypotension?

Hypotension usually gets better by treating the underlying health condition. The goal is to raise blood pressure and reduce the signs and symptoms. The following measures are helpful:

  • More salt in food as sodium is known to raise blood pressure.

  • Drink a lot of fluids to prevent dehydration.

  • Compression stockings reduce the pooling of blood in the legs seen in postural hypotension.

  • For orthostatic hypotension, medications like Fludrocortisone and Midodrine can help.

How Can Hypotension Be Prevented?

The symptoms caused by low blood pressure can be prevented by:

  • Drinking more water.

  • Consuming less alcohol.

  • Take a healthy diet.

  • Eat small meals and a low-carbohydrate diet.

  • While getting up from the bed in the morning, take a few deep breaths and stand up after sitting for some time.

You can learn how to prevent and manage the symptoms effectively by identifying the triggers, and by trying to avoid them as much as possible. Keep monitoring your blood pressure at home, and if it remains low the majority of times and if it is causing symptoms, consult a cardiologist online.

Last reviewed at:
14 Oct 2019  -  5 min read


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