Last updated date: 11-Mar-2024

Originally Written in English

Causes of Low Blood Pressure (Hypotension)

  • General Health

  • Hypotension

  • Low Blood Pressure

Low blood pressure (Hypotension)

Hypotension is defined as a drop in systemic blood pressure below acceptable low levels. While no agreed standard hypotensive value exists, pressures less than 90/60 mmHg are considered hypotensive. Hypotension is a very harmless ailment that goes unnoticed since it is usually asymptomatic. It only becomes a problem when the pumping pressure is insufficient to provide oxygenated blood to vital organs.


How is blood pressure measured?

Blood pressure is determined by two main mechanisms: cardiac output and total peripheral vascular resistance. As a result, any pathological illness that affects one or both these parameters will cause hypotension.

Blood pressure is measured with a device known as a sphygmomanometer which has an attached stethoscope. The stethoscope helps in hearing the Korotkoff sound produced by back and forth pulses.

Blood pressure is defined as:

  • Blood Pressure = Cardiac output x Total peripheral vascular resistance
  • The mean arterial pressure is an average blood pressure over the course of one cardiac cycle. It is calculated as:
  • Mean arterial pressure = 2/3 diastolic pressure + 1/3 systolic pressure



LOW BLOOD PRESSURE: 90/60mmHg or lower

HIGH BLOOD PRESSURE: 140/90mmHg or higher


Disease conditions that lower stroke volume or heart rate reduce the overall cardiac output of the heart, reducing its functional ability to create blood pressure. Various drugs might also cause hypotension by influencing certain biologic markers. The beta-blocker and calcium channel blocker groups of medications are the most well-known for lowering heart rate.

In healthy people, both cardiac output and total peripheral vascular resistance serve as feedback compensation mechanisms for one another. When cardiac output falls, peripheral resistance should rise by constriction of terminal arterioles to reduce artery diameter in order to maintain blood pressure. When peripheral resistance diminishes, cardiac output increases through higher heart rate in order to maintain blood pressure.

Acute life-threatening illness processes are conceivable and are characterized as distributive shock, cardiogenic shock, hypovolemic shock, obstructive shock, or a combined-type hypotensive shock based on etiology.


Types of hypotension

  • Orthostatic hypotension

Orthostatic hypotension is also known as postural hypotension. This is referred to as an immediate fall in blood pressure which occurs as a result of standing up too quickly. 

When you stand up suddenly, gravity drags the blood down to your legs. This interrupts the normal circulation of blood and blood pressure begins to fall down. 

  • Neurally mediated hypotension 

Neurally mediated hypotension (NMH) is also termed as vasovagal syncope or fainting reflex. It occurs as a result of prolonged standing. When you stand for a long time, the blood pools in your feet and legs. This reduces the flow of blood towards your heart, brain, and other organs.

  • Hypotension shock (Severe Hypotension)

When your body organs do not get enough oxygen due to low blood pressure the patient usually gets faint and undergoes a shock. If severe hypotension is not treated promptly, it can be life-threatening.

Distributive shock is caused by a failure to maintain complete peripheral resistance while maintaining heart activity in an attempt to compensate. Warm extremities and skin, edema, increased mucous secretions, and tachycardia are typical symptoms. This is commonly linked to anaphylactic allergic responses and septic shock.

Cardiogenic shock is defined as a failure to deliver enough cardiac output while maintaining total peripheral resistance. These individuals typically appear with chilly, dry extremities and skin, as well as bradycardia.

Hypovolemic shock is defined as a reduction of total blood volume to the point that blood pressure cannot be maintained. The cardiac output and total peripheral vascular resistance remain constant. This is happens as a result of trauma resulting in substantial blood loss or through misuse of diuretic drugs resulting in fluid volume loss via urine.

Cortisol shortage, as found in Addison disease, causes fluid loss through urine as well as a relative cortisol shortage. Sheehan syndrome is characterized by postpartum pituitary necrosis, which results in the loss of several pituitary hormones as a result of postpartum shock or bleeding.


Obstructive shock occurs when the circulatory system is obstructed, constricted, or compressed, resulting in inefficient blood flow or a decrease in heart stroke volume. This results in a systemic reduction in blood pressure. Obstruction can arise as a result of a pulmonary embolism, tension pneumothorax, cardiac tamponade, constrictive pericarditis, or another kind of restrictive cardiomyopathy.

Congestive failure symptoms such as dilated jugular veins, peripheral edema, pulmonary crackles, silent heart sounds, or pulsus paradoxus are typical. 

Hypotensive shock can also arise as a result many of the aforementioned diseases happening at the same time. Waterhouse-Friderichsen syndrome, for example, is an adrenal-gland failure to generate mineralocorticoids, glucocorticoids, and sex hormones caused by frank bleeding into the adrenal glands as a result of bacterial infection by Neisseria. This results in a slew of hypovolemic and distributive shock symptoms.



The exact epidemiology of hypotension is quite diverse and is determined by the cause. In general, aged people are more likely to experience non-traumatic, symptomatic hypotension. Patients who are more physically active and healthy will also have lower resting asymptomatic blood pressures.



Blood pressure is constantly controlled by the autonomic nervous system, which is a balance of the sympathetic and parasympathetic nervous systems. By raising heart rate and constricting arterioles, the sympathetic nervous system raises blood pressure. The parasympathetic nervous system decreases blood pressure by slowing the heart rate and relaxing arterioles, allowing vessels to dilate.


Causes of low blood pressure

Causes of low blood pressure

Low blood pressure is not uncommon these days. In order to overcome it, it is very important to know its causes. Some of the common causes of low blood pressure may include:

  • Inappropriate diet
  • Low carbohydrate diet
  • Alcohol intake
  • Lack of vitamin B12 
  • Lack of vitamin B9 (folic acid)


Other factors and underlying diseases that can cause low blood pressure may include:

  • Post Exercise   

Low blood pressure which is experienced after acute exercise is termed as Post Exercise Hypotension or PEH. After hectic exercise, vasodilator substances get introduced into our vessels and vascular resistant substances get diminished due to which proper constriction is not achieved. Lack of constriction ultimately leads to low blood pressure.

  • Dehydration

Sometimes, dehydration can be a contributing factor to the onset of low blood pressure. Dehydration may happen as a result of frequent urination, profuse sweating, lack of water intake, vomiting, fever, and diarrhea.

  • Infections

When a virus or bacteria enters our body, our immune system secretes fighting agents such as cytokines, macrophages, and interleukins. These fighting agents lead to vasodilation causing our blood pressure to drop.

  • Bradycardia

Bradycardia or low beating of the heart is considered one of the major causes of low blood pressure. Those who are experiencing bradycardia may complain about frequently occurring hypotension.

  • Anemia

Anemia is a medical condition in which the amount of healthy blood cells becomes reduced and subsequently, the body tissues do not get enough oxygen. Inadequate supply of oxygen results in the onset of low blood pressure. This primarily occurs due to deficiency of vitamin B12, iron, and vitamin B9 (folic acid).

See more information: All you need to know about anemia

  • Anaphylaxis

Anaphylaxis is also termed anaphylactic shock. It is an allergic reaction that takes place due to some particular food items and medications. During anaphylactic shock, vasodilators are secreted out, blood tissues do not get enough oxygen, and blood pressure drops.

  • Medications 

It is very important to take a prescription from your doctor before starting off with any kind of pills. There are a few medications that are known to cause hypotension such as:

  1. Diuretics
  2. Antidepressants
  3. Anesthetic drugs
  4. Midazolam
  5. Nitric oxide
  6. Levodopa
  7. Antipsychotics


  • Diabetes Mellitus

Those who are prone to diabetes may complain about frequently occurring hypotension. This happens because diabetes causes frequent urination leading to dehydration and ultimately dropping down the blood pressure. 

  • Addison’s disease

Addison's disease is a medical condition that is caused by adrenal insufficiency. In this disease, the body becomes unable to absorb sodium due to large amounts of sodium being excreted out. When sodium is excreted out from our body, it takes out a large amount of water along with it, resulting in dehydration. This dehydration becomes a contributing factor to low blood pressure. 

  • Parathyroid carcinoma

Any tumor in the parathyroid gland is known as parathyroid carcinoma. The function of the parathyroid gland is the absorption of calcium and the excretion of phosphorus. When parathyroid removes phosphorus from the body, it takes out water along with it. Lack of water may lead to hypotension or low blood pressure. 

  • Renal problems

The kidney is a major organ of homeostasis. When kidneys do not get a sufficient amount of blood, they become unable to get adequate oxygen. Lack of oxygen triggers hypotension. 

  • Malaria

Studies have shown that malaria can highly impact the blood pressure regulatory system, causing hypotension and other disorders of blood pressure. Patients diagnosed with malaria are more susceptible to be attacked with low blood pressure problems.

  • Pheochromocytoma

Pheochromocytoma is a tumor of the renal medulla. The renal medulla is a part of our kidneys that secretes epinephrine (a vasoconstrictor). 

Pheochromocytoma disease reduces the amount of epinephrine secretion. A reduced amount of epinephrine cause vasodilation eventually leading to hypotension. 

  • Aldosterone deficiency

Aldosterone is a hormone that helps in the absorption of salt. When aldosterone becomes insufficient, the amount of salt absorption drops. Low salt absorption is proven to be one of the major causes of low blood pressure. 

  • ADH deficiency

ADH or Antidiuretic hormone is also known as vasopressin. Vasopressin controls blood pressure by acting on blood vessels and kidneys. It functions to conserve enough water in the body. 

Deficiency in the amount of antidiuretic hormone reduces the water content in the body causing dehydration and eventually leading to hypotension. 

  • Hemorrhage

Loss of blood due to injury or trauma is termed as hemorrhage. Hemorrhage leads to hypovolemic conditions or reduced blood content in the body. As the amount of blood content gets reduced, the patient becomes more prone to hypotension or low blood pressure.

  • Cerebral edema

Cerebral edema is a medical term used for swelling of the brain. Swelling may occur in response to some injury or damage. In this condition, fluids get built up around the brain restricting the supply of oxygen. When tissue runs short of oxygen, the chances of hypotension are increased. 

  • Pituitary gland insufficiency

The pituitary gland is an endocrine gland that functions to secrete hormones such as anti-diuretic hormone (vasopressin) and aldosterone. Insufficiency of the pituitary gland reduces the secretion of these hormones, which results in the excess excretion of salt and water out of the body, eventually leading to the conditions of low blood pressure. 

  • Proteinuria      

Proteinuria is a medical condition in which an excessive amount of proteins are excreted out of the body through urine. Proteins are essential to be present in the right amount for the regulation of fluids in the body. When proteins enter the urine, they eventually leave the body which is absolutely not healthy. 

This leads to frequent urination thus causing dehydration. Dehydration then contributes to the onset of low blood pressure conditions. 


Low blood pressure symptoms

Signs and symptoms of low blood pressure may include:

  • Dementia (memory loss)
  • Nausea
  • Fainting
  • Lightheadedness
  • Increased heart rate
  • Blurred vision
  • Pale skin
  • Dry tongue
  • Headache
  • Weakness

Chronic conditions of hypotension can also show serious symptoms such as muscle cramps, muscle strain, muscle spasms, seizures, and convulsions.



The evaluation is based on the suspected reason. Thyroid-stimulating hormone (TSH), free t4, and cortisol levels, as well as a complete blood count (CBC) with differential, can be ordered. If a patient is in shock, a STAT echocardiography with inferior vena cava (IVC) variability, combined with stabilizing interventions, can be performed. The left ventricular ejection fraction will be determined using echocardiography.

Pressures in the right ventricle, as well as the presence or absence of pericardial effusion. If the patient's left ventricular ejection fraction (LVEF) and right ventricular function are acceptable and he or she is in distributive shock, the inferior vena cava (IVC) variability test will aid in fluid resuscitation management. The optimum fluid resuscitation regimen is determined using pulse pressure fluctuation.


Low blood pressure treatment

Low blood pressure treatment

Asymptomatic hypotension should not be treated with harsh measures. However, if symptoms are evident, hypotension therapy should focus on treating the underlying cause. Noninvasive imaging or hemodynamic markers of reduced cardiac output or systemic vascular resistance are not diagnostic criteria but may aid in the classification of hypotension. As a result, an ECG, echocardiography, and chest X-ray may be useful in the workup.

It is very important to consult a doctor if you feel any of the aforementioned symptoms. Here are a few approaches which can be helpful for low blood pressure. 

  • Salt intake

Salt is a major constituent of external cellular fluid (ECF). As the studies and researches have proven, low salt intake can cause low blood pressure. This is why it is necessary to balance our salt intake. Increased intake of salt is a successful strategy to recover blood pressure. 

  • Increased water intake

More than 60% of the human body is composed of water. As research has shown that inadequate amounts of water make our blood viscous ultimately leading to low blood pressure. So, increased water intake can be a great help. 

  • Stop Alcohol

Alcohol increases urination thus excreting a lot of water out of the body. Excess excretion of water causes serious dehydration. It is recommended to cut down on drinking alcohol in order to prevent the onset of hypotension. 

  • Balanced diet

Try to get a food chart from your doctor to maintain your diet. A balanced diet is very important for the prevention of hypotension. Consume some salt and folate-rich foods. Drink plenty of fluids. Try eating olives, cottage cheese, pickled items, smoked fish, snack foods, and canned soup. 

  • Quit smoking

Smoking is lethal and injurious to health. It interferes with the body's ability to absorb nutrients and makes our blood thick. It reduces the capability of hemoglobin to provide enough oxygen. Inadequate oxygen supply causes blood pressure to drop. It is highly recommended to stop smoking as a preventive measure.

  • Medications

If you suffer from consistent hypotension, you should seek medical attention as soon as possible. Untreated hypotension can cause serious medical conditions and complications. It can even be lethal if it becomes persistent. 


Low blood pressure emergency treatment 

An extended focused assessment with sonography in trauma (e-FAST) test may be useful in identifying the existence of intracavitary bleeding in a trauma case with hypotension and no obvious blood loss. Urine output should be monitored to ensure that fluid resuscitation efforts are adequate, with an output of 0.5 to 1.0 mL/Kg per hour.

Along with fluid resuscitation, fluid electrolytes must be monitored and replaced as needed to prevent creating an abnormality. Orthostatic vital signs may also aid in diagnosis. If a drug is suspected of being the cause, the medication should be stopped. Rapid fluid resuscitation with bleeding stoppage is critical in acute shock situations.

If the mean arterial pressure is less than 65 mm Hg, vasopressors may be prescribed. Serial blood cultures and early antibiotics are required if sepsis is suspected. Intramuscular epinephrine is required if anaphylaxis is suspected. When a patient's vasopressor need is constantly growing and proper fluid resuscitation has been performed, adding steroids to treat distributive shock will help to maintain blood pressure as well. 


Low blood pressure effects 

While hypotension is not generally a dangerous medical condition, it can result in accidents due to fainting and falling. If hypotension is not addressed, the brain, heart, and other organs will not receive enough blood and will be unable to function correctly. Severe hypotension can result in a deadly shock.


Low blood pressure for elderly

Low blood pressure is less prevalent in the elderly than high blood pressure and is typically considered an issue only if it produces symptoms. If you feel dizzy, lightheaded, or weak, this might be an indication that your blood pressure is too low and you should consult a doctor.


Low blood pressure during pregnancy

Low blood pressure is a common condition during pregnancy. Blood pressure is frequently reduced by fluctuating hormones and changes in circulation, particularly during the first and second trimesters of pregnancy.

Low blood pressure might occasionally be a sign of another issue. It might be the outcome of an ectopic pregnancy, in which a fertilized egg implants itself outside of your uterus. And if it's really low, it can lead to falls or shock, in which your brain and other essential organs don't receive enough blood to function correctly.                                                                                                                                                                                                                                                                                    

Differential Diagnosis

  • Benign hypotension
  • Distributive shock
  • Cardiogenic shock
  • Hypovolemic shock
  • Obstructive shock
  • Combined-type hypotensive shock



The prognosis for benign hypertension is excellent. The prognosis of symptomatic hypotension varies depending on the cause and severity.



The complications of untreated hypotension with low cardiac output are severe and can result in death. Untreated hypotension in imminent or fulminant shock might result in multi-organ failure. To avoid these consequences, current guidelines for treating patients with shock or impending sepsis emphasize aggressive and sufficient fluid resuscitation.



Low blood pressure is a serious medical condition that should not be overlooked. Although there is no agreed standard hypotensive value, pressures below 90/60 mmHg are considered hypotensive. Hypotension is a relatively benign condition that goes unnoticed since it is usually asymptomatic. It only becomes a problem when the pumping pressure is insufficient to properly perfuse vital organs.

This results in symptoms that have an influence on the patient's quality of life. It can be due to several factors and pathologies, an etiological diagnosis is essential especially in acute or severe cases.

Asymptomatic hypotension in outpatients does not require treatment. In case of shock or severe hypotension, the use of resuscitation is mandatory and treatment should focus on treating the underlying cause. The prognosis depends on the rapidity of treatment and the etiology.