Causes of Low Blood Pressure
There are many causes of low blood pressure. Severity of low blood pressure ranges from mild (e.g. in simple faints) to severe low blood pressure in various types of shock. All types of shock are a medical emergency.
Common Causes of Mild Hypotension: Some of the common causes of mild levels of low blood pressure, such as those causing fainting, include:
- Normal blood pressure. The range of normal varies somewhat. Some people have normal blood pressure readings that would be considered low for others.
- Emotional stress. Sudden emotional shock can cause low blood pressure and fainting.
- Postural hypotension (autonomic nerve disorders)
- Mild dehydration
- Fainting disorders (see also: causes of fainting)
- Mild arrhythmias (e.g. palpitations)
- Vasovagal attack (vasovagal syncope)
Some of these disorders can be dangerous in more severe cases. Various other causes of fainting are possible. Note also that some types of fainting disorders are serious and can result in unconsciousness, syncope, shock, etc., rather than a simple faint. A faint can also cause an injury from a fall. Read more about: Fainting.
- Anaphylactic shock (allergic reactions)
- Severe dehydration
- Hypovolemic shock (Hypovolemia; low blood volume). Often caused by dehydration or blood loss from injury or accident.
- Septic shock (sepsis; septicemia)
- Neurogenic shock
- Cardiogenic shock
- Inadequate water intake
- Severe vomiting
- Severe diarrhea
- Excessive urination
- Diuretic medications
- Internal bleeding
- Gastrointestinal bleeding
- Head Injury. Intracranial bleeding may cause hypovolemia in infants or children, but is not normally enough blood loss to cause hypotension in adults (though it causes high ICP and other life-threatening effects in all patients).
- Hemorrhage (blood loss)
- Diarrheal disorders
- Vomiting disorders
- Diabetic Ketoacidosis. This life-threatening medical emergency causes severe dehydration and is usually caused by Type 1 diabetes (undiagnosed or poorly controlled).
- Hyperosmolar Hyperglycemic Nonketotic Syndrome (HHNS). Similar to DKA, this life-threatening disorder causes dehydration and is usually from undiagnosed or poorly controlled cases of Type 2 Diabetes (i.e. the other type of diabetes).
- Metabolic disorders (generally)
Heart Disorders: Various disorders of the heart and its related systems can cause low blood pressure, from mild to severe cases, such as:
- Arrhythmias (Cardiac rhythm disorder)
- Heart attack (myocardial infarction)
- Cardiac insufficiency (low cardiac output)
- Heart failure
- Congestive heart failure
- Heart muscle disorder
- Cardiac contusion
- Cardiac tamponade
- Cardiogenic shock
- Cardiac disorder (various types)
- Hypoperfusion disorders
Drugs and Toxic Causes: Various drugs and substances can affect the blood pressure system, resulting in low blood pressure:
- Alcohol intoxication (alcohol poisoning)
- Medication side-effect
- Drug interaction. The use of multiple drugs often causes hypotension as a side effect.
Medical Test Causes: Some types of medical testing can cause low blood pressure:
- Diagnostic contrast test side-effect (or allergic reaction)
- Gastric acid stimulation test (histamine adverse reaction)
- Normal variation. Some people have lower blood pressure naturally, without any abnormality.
- Athletic fitness. High levels of fitness often result in low blood pressure.
- Orthostatic hypotension
- Fainting disorders
- Addison’s disease
- Autonomic nerve disorders
- Diabetic neuropathy (autonomic neuropathy)
- Spinal cord injury
- Brain injury
- Cardiovascular disease
- Heart failure
- Aortic stenosis
- Mitral valve disorder
- Vasodilator medications
- Blood pressure medications (antihypertensives)
- Medication side-effects (various medications can cause chronic hypotension).
Other Causes: Various other causes of low blood pressure may include:
- False blood pressure reading. An incorrectly placed measurement cuff, or an incorrectly large cuff used for measurement (“small cuff syndrome”), such as in children, may cause a falsely low reading.
- Post-surgical hypotension (e.g. due to vasodilation effects from anesthetic medications)
- Adrenal insufficiency
- Adrenal crisis
- Postprandial hypotension
- Neurologic disorders
Similar Symptoms: See also the causes of similar symptoms such as:
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Note: This site is for informational purposes only and is not medical advice. See your doctor or other qualified medical professional for all your medical needs.