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What Causes Low Blood Pressure?

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Updated September 26, 2013

Question: What Causes Low Blood Pressure?
Answer:

Many things can cause your blood pressure to be too low, ranging from normal pregnancy-induced changes to dangerous underlying conditions, like heart problems or hormone disturbances. In some instances, what causes low blood pressure could be a simple case of dehydration brought on by vomiting, intense exercise, or the overuse of diuretics. Some studies have shown that a dehydration-induced weight loss of 1 percent is enough to trigger dizziness, confusion, or other symptoms of low blood pressure.

One especially important cause of low blood pressure is orthostatic hypotension, which is sometimes referred to as postural hypotension. This happens when blood pressure drops rapidly during changes in body position — usually when changing from sitting to standing — inducing classic signs that the blood pressure is too low, like dizziness, blurry vision, and fainting.

Other important causes of low blood pressure include:

  • Heart problems that cause low heart rate, diminished heart strength, or a decrease in the amount of blood supplied to the body
  • Normal changes associated with the first and second trimesters of pregnancy
  • Side effects from certain medications, especially diuretics or other high blood pressure medications, like beta blockers. Medicines used to treat erectile dysfunction and certain psychiatric disorders can also cause low blood pressure.
  • Hormone problems such as adrenal insufficiency or thyroid disease (overactive or underactive thyroid)
  • Problems with the nervous system--especially disorders of the autonomic nervous system, including POTS and vasovagal syncope--can cause low blood pressure after extended periods of standing.
  • Deficiencies of essential nutrients, such as folic acid, can cause the number of red blood cells to decrease (anemia)
  • Alterations in blood sugar, like those caused by diabetes
  • Age: Some older patients, especially those with existing high blood pressure, can experience postprandial hypotension, where the blood pressure drops suddenly after eating a large meal
While most cases of low blood pressure are not considered medical problems, cases where the low blood pressure is accompanied by symptoms should always be evaluated by a physician. A complete medical workup will often be needed in order to rule out the possibility of an underlying disorder.

More About Low Blood Pressure:

Sources:

  1. Christensen KL, Mulvany MJ. Vasodilatation, Not Hypotension, Improves Resistance Vessel Design During Treatment of Essential Hypertension: A Literature Survey.Journal of Hypertension. 2001 Jun;19(6):1001-6.
  2. Palma Gamiz JL, et al. Iberian Multicenter Imidapril Study on Hypertension: A twelve-week, multicenter, randomized, double-blind, parallel-group, noninferiority trial of the antihypertensive efficacy and tolerability of imidapril and candesartan in adult patients with mild to moderate essential hypertension: the Iberian Multicenter Imidapril Study on Hypertension (IMISH).
  3. Shin DD, et al. Review of Current and Investigational Pharmacologic Agents for Acute Heart Failure syndromes. American Journal of Cardiology. 2007 Jan 22;99(2A):4A-23A.
  4. Verheij J, et al. Cardiac response is greater for colloid than saline fluid loading after cardiac or vascular surgery. Intensive Care Medicine. 2006 Jul;32(7):1030-8.
  5. Eldadah BA, et al. Failure of propranolol to prevent tilt-evoked systemic vasodilatation, adrenaline release and neurocardiogenic syncope. Clinical Science (London). 2006 Sep;111(3):209-16.
  6. Naschitz JE, Slobodin G, Elias N, Rosner I. The patient with supine hypertension and orthostatic hypotension: a clinical dilemma.Postgraduate Medical Journal. 2006 Apr;82(966):246-53.
  7. Tipre DN, Goldstein DS. Cardiac and extracardiac sympathetic denervation in Parkinson's disease with orthostatic hypotension and in pure autonomic failure. Journal of Nuclear Medicine. 2005 Nov;46(11):1775-81.
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  6. What Causes Low Blood Pressure, or Hypotension?

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