What Are the Causes of Low Blood Pressure?

By Marie Louise

Blood pressure is measured as a systolic and diastolic number. A normal blood pressure is 120/80. The systolic, or upper number, is the measure of pressure in the arteries as the heart contracts. Diastolic measures the pressure when the heart rests. Low blood pressure is classified as a reading below 90/60. Low blood pressure is considered a problem when there are symptoms with it. Some people have low blood pressure normally and have no symptoms.

Endocrine System

The endocrine system uses hormones from the thyroid, pituitary and adrenal glands to regulate functions in the body. Low blood pressure can be caused by hypothyroidism. Too little thyroid hormone slows down the functions of the body including blood pressure and metabolism. The hormones produced by the adrenal glands have a part in controlling some of the body's functions such as blood pressure, heart rate and metabolism. Addison's disease is an adrenal gland dysfunction that can cause low blood pressure. Other endocrine system problems that could cause low blood pressure is a pituitary gland that doesn't produce enough hormone and people with diabetes can suffer hyperglycemia and low blood pressure if their blood sugar drops.


Dehydration can cause low blood pressure called orthostatic hypotension, also known as postural hypotension. Dehydration occurs when you lose more water in the body than can be put back in. This can be due to illness, strenuous physical activities or not replacing fluids in extremely hot weather.


Diuretics, also called water pills, given at higher dosages can cause low blood pressure because they remove water from the body. Diuretics are typically prescribed for high blood pressure. Medications such as calcium channel blockers, antidepressants, ACE inhibitors and alpha blockers dilate arteries and veins, causing low blood pressure.


Septicemia is an infection that goes into the bloodstream. This type of infection can cause septic shock, which causes the blood pressure to drop dramatically. This can be life-threatening and left untreated can be fatal.

Lack of Nutrients

Low levels of the vitamin B12 can result in anemia. Anemia is caused by low levels of iron in the blood. Anemia and B12 can keep the body from producing enough red blood cells to carry adequate oxygen through the body. Combined, these conditions can cause low blood pressure.

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