Why Does Blood Pressure Drop?


Did you know that being married can cause low blood pressure? Did you know that hypertension affects at least 20% of the population at some point?

According to the National Heart, Lung, and Blood Institute, low blood pressure occurs when blood flows through blood vessels at lower than normal pressures and it is called hypotension. Pressure is created when blood pushes against the walls of the arteries and this is measured in millimetres of mercury. Blood pressure is made up of two types of pressure, systolic pressure- when the heart contracts- and diastolic pressure- when the heart relaxes.  A normal blood pressure reading is 120/80 mmHg (systolic/diastolic), while a reading of 90/60 mmHg and below constitutes low blood pressure.

Low blood pressure may be normal for many people, but it is oftentimes due to an underlying health problem related to the heart and brain like a stroke or impending heart attack. Other health-related causes of low blood pressure may include diabetes, dehydration, high blood pressure medications, and Parkinson's disease. Usually, more importance is given to high blood pressure than low blood pressure. Dizziness and giddiness and unexplained tiredness in women and men are signs of low systolic blood pressure. Other symptoms also include headaches and mental health issues like anxiety and depression.


  1. Pregnancy can give rise to hypotension in the first two trimesters. This happens as the circulatory system (arteries and veins) expands to supply the uterus and placenta.
  2. Heart problems unlike normal conditions can progressively reduce hypotension like low heart rate or Bradykardia, heart attack, or heart failure. 
  3. Health problems - Diabetes mellitus and endocrine problems are common problems associated with low blood pressure. Spinal cord lesion, ageing, nerve growth deficiency, neurological disorders, prion-mediated disease. It can also be seen in cancer and in AIDS.
  4. Dehydration - Factors like extreme heat and dehydration can cause or increase hypotension. It is better to increase salt and water intake. Patients must eat smaller meals and avoid alcohol as this has effects of increasing low blood pressure and dehydration respectively. 
  5. Blood loss due to internal bleeding or other injuries results in low blood pressure
  6. Severe infection or Septicemia - Hypotension occurs when there is a septic shock due to severe infection in the bloodstream. 
  7. Severe allergic reaction- All you need is itching and hives from medications, and foods for an Anaphylactic shock and this can cause low blood pressure. 
  8. Lack of nutrients - If your diet lacks iron, Vitamin B12 and folate, you become prey to low blood pressure as a result of abnormal blood cells and low blood pressure due to an oxygen-transporting obstacle.
  9. Medications that affect vascular regulation, peripherally acting agents like prazosin, gunaneine, angiotensin-converting enzymes and beta blocking agents.

Other causes of hypotension

Many diseases are responsible for hypotension, it's not a one-man band, due to myriad problems like reduced blood volume, drug-induced hypotension, miscellaneous disorders, and autonomic disorders.

Reduced effective blood volume can be due to acute and subacute intravascular volume losses caused by: 

  • Haemorrhage 
  • Burns
  • Sepsis
  • Dialysis
  • Hyperglycemia
  • Diabetes Insipidus

Other health issues with can cause hypotension include:

  • Intravascular volume contraction in Addison's disease
  • Diarrhoea, especially in cholera, 
  • Renovascular hypertension
  • Salt-losing nephropathy
  • Anorexia nervosa
  • Intravascular volume in hyperthyroidism
  • Mitral valve prolapse. 

Medications well known to cause hypotension include:

  • Tricyclic depressants
  • Diuretics
  • Sympatholytics
  • Minor tranquillisers
  • Nitrates
  • Insulin
  • Alcohol
  • Narcotic agents
  • Sympathomimetic agents
  • Marijuana
  • Vasodilators

Other causes of hypotension include cardiac arrhythmias, angina, heart failure, prolonged bed rest, contraction of circulatory volume during the third trimester of pregnancy and weightlessness. 

Neurogenic causes of hypotension include peripheral neuropathies, lesions and surgeries of the spinal cord, multiple sclerosis, Parkinson's disease and cerebellar degeneration. Acquired immunodeficiency syndrome (AIDS) can also cause neuropathy and hypotension. 

Psychiatric disturbances, deficits caused by irradiation, surgical treatment, and tumours can cause orthostatic hypotension. In addition, increased ocular pressure, micturition, and myocardial ischemia can all result in hypotension. 

Nutritional deficiencies such as vitamin B12 and folate, renal failure and systemic collagen vascular disease are other factors that cause hypotension. 

It should be noted that in cases of Diabetes insipidus, Riley Day syndrome and Dopamine -beta-hydroxylase deficiency, baroreceptor dysfunction causes chronic orthostatic hypotension. (9,10,11)

Causes for a sudden drop in blood pressure

Dehydration, loss of blood from bleeding, low body temperature, high body temperature, sepsis, heart failure, and reaction to alcohol or medications can cause a deviation from normal blood pressure. 


Symptoms of blood pressure include 

  • lightheadedness, 
  • fatigue, 
  • dizziness, 
  • tiredness, 
  • confusion, 
  • general weakness, 
  • depression  
  • dehydration and excessive thirst (sometimes). 

Some additional symptoms included parkinsonian symptoms, frequent UTIs, sleep apnea and diffuse neurologic deficits. 

How to check the blood pressure

A physical examination will show a drop in systolic pressure by 25 mm Hg and 10 mm Hg of diastolic pressure in a minute of standing upright and is a reliable estimate of underlying hypotension conditions. The patients also exhibit clinical symptoms concomitantly. Moreover, the eye examination can reveal mitotic vision that cannot dilate with pain. Tremor, pale skin with rigidity and paucity of movement are additional signs.

An exact estimate with physical examination for underlying physiological and pathological disorders must be done; checking for malignancy and heart failure, a mental status examination to detect dementia, Parkinsons and sensory testing. This includes laboratory blood tests that include haemoglobin and hematocrit levels for detecting electrolytes, anemia, urea nitrogen and creatinine for dehydration, a test for syphilis, and a glucose tolerance test for detecting diabetes. Additional brain imaging studies must be ordered if there is suspicion of central nervous system failures.

Types of hypotension

Orthostatic hypotension

According to Mayoclinic.com, this is also known as postural hypotension.(1) It is the drop in blood pressure as a result of the sudden change from a sitting or lying position to a standing position. This happens because gravity causes blood to pool in the legs while standing up. The body compensates by increasing heart rate and constricting blood vessels for the blood to flow to the brain in normal conditions but in hypotension, this does not happen. Low blood pressure and high blood pressure, the same difference but different causative factors can be chronic and acute and occur during pregnancy, dehydration, heart problems, burns, excessive heat or on taking medications like diuretics, beta-blockers, drugs for Parkinson's and erectile dysfunction.

Postprandial hypotension

This is a drop in blood pressure after eating.  This drop in blood pressure occurs one to two hours after eating. This affects older people, people with Parkinson's disease, and high blood pressure. It occurs when blood cannot travel to the digestive tract as normally and is impeded by constricting blood vessels. Small meals, drinking more water, and low carb meals can help with symptoms. 

Neutrally mediated hypotension

Faulty brain signals cause this type of hypotension. It occurs in adults and young children. It is because of a miscommunication between heart and the brain.

Multiple system atrophy with orthostatic hypotension

This is also called Shy-Drager syndrome. This health condition has symptoms like Parkinson's disease. Blood pressure, heart rate, breathing and other activities are damaged in autonomic nerve system 


Moderate low blood pressure can cause mild symptoms that include injury from falls. Chronic and acute hypotension can damage the heart and brain by causing irreversible changes as a result of insufficient oxygen supply. How to regulate your blood pressure:

  • Use more salt - Salty foods can be beneficial for patients with low blood pressure but definitely in the lower range. Low blood pressure benefits from increasing salt in their diet but since salt is dangerous for older adults because of heart associated complications, consultation with the doctor is mandatory before altering the diet. 
  • Drink water - Dehydration can cause low pressure. One must drink lots of water; this has no effect on blood pressure but it increases blood volume. 
  • Compression stockings - Wearing nothing but compression stockings for relieving varicose veins can work for low blood pressure. This increases blood pooling in the legs.
  • Medications - Fludrocortisone is the best medicine for hypotension. This can treat orthostatic hypotension by increasing blood volume. Other drugs like Orvaten are also used to improve  chronic orthostatic hypotension and its way of acting is through preventing expansion of blood vessels.


Low blood pressure is a disease and can be of various types. The primary causes include co- morbidities like neuronal diseases like Parkinson’s, multiple sclerosis and psychiatric disturbances. The even odds of low blood pressure with a metabolic disease like diabetes, dehydration and cardiac diseases like myocardial infarction, ischemic are additional factors. It's important to understand the reason for low blood pressure and get proper treatment for this condition. It can be monitored at home and treated with simple steps like increasing salt in the diet. 


  1. Low blood pressure (hypotension) - Symptoms and causes [Internet]. Mayo Clinic. 2022 [cited 13 April 2022]. Available from: https://www.mayoclinic.org/diseases-conditions/low-blood-pressure/symptoms-causes/syc-20355465.
  2. The Basics of Low Blood Pressure [Internet]. WebMD. 2022 [cited 13 April 2022]. Available from: https://www.webmd.com/heart/understanding-low-blood-pressure-basics
  3. Advancing Heart, Lung, Blood, and Sleep Research & Innovation | NHLBI, NIH [Internet]. Nhlbi.nih.gov. 2022 [cited 13 April 2022]. Available from: http://nhlbi.nih.gov
  4. Gupta V, Lipsitz LA. Orthostatic hypotension in the elderly: diagnosis and treatment. Am J Med. 2007 Oct;120(10):841-7. doi: 10.1016/j.amjmed.2007.02.023. PMID: 17904451.
  5. Chisholm P, Anpalahan M. Orthostatic hypotension: pathophysiology, assessment, treatment and the paradox of supine hypertension. Internal Medicine Journal. 2017;47(4):370-379.
  6. Wessely S, Nickson J, Cox B. Symptoms of low blood pressure: a population study. 2022.
  7. [Internet]. 2022 [cited 13 April 2022]. Available from: https://www.sciencedaily.com/releases/2008/03/080320192610.htm
  8. [Internet]. 2022 [cited 13 April 2022]. Available from: https://www.sciencedaily.com/releases/2008/03/080320192610.htm
  9. Orthostatic Hypotension - an overview | ScienceDirect Topics [Internet]. [cited 2022 Jul 28]. Available from: https://www.sciencedirect.com/topics/veterinary-science-and-veterinary-medicine/orthostatic-hypotension.
  10. Goldstein DS. Dysautonomia in Parkinson’s disease: neurocardiological abnormalities. Compr Physiol [Internet]. 2014 [cited 2022 Jul 28]; 4(2):805–26. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4222515/.
  11. Palma J-A, Kaufmann L, Fuente C, Percival L, Mendoza C, Kaufmann H. Current Treatments in Familial Dysautonomia. Expert Opin Pharmacother [Internet]. 2014 [cited 2022 Jul 28]; 15(18):2653–71. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4236240/.

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Aarthi Narayan

Master of Science (M.S.), Biological science, University of Illinois Chicago
Scientist with 10+ years of strong industry, academic experience in Molecular biology, Tissue culture, Protein purification techniques. Mid-level experience in Diagnostics and start-ups. Excellent at completing large scale projects and experiments with minimal supervision in a timely and efficient manner.

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