Causes of Low Blood Pressure
Are Numerous

There is not one of these causes of low blood pressure that you would want to any degree. They range from the self limiting to the dangerous to the downright lethal. From the self-limiting simple fainting (common) to the complex nervous system disorders (uncommon), they cover a wide variety of disease states.

Why compare low blood pressure to quicksand? Because it starts hurting your different organ systems and topples them over in succession thus pulling you down and down. Not a pretty scene.

The causes of low blood pressure can be classified by how they effect the regulatory system of blood pressure. For an overview of this subject see Normal Blood Pressure

Causes of Low Blood Pressure:

First we have the change in regulatory mechanism and underneath it are the disease states that cause it.

  1. Decreased cardiac output:

    • Abnormal heart rhythms.
    • Heart muscle damage (heart attack or myocardial infarction).
    • Heart muscle weakness (virus, alcohol).
    • Heart valve disorder (obstruction or leaking).
    • Pulmonary embolism.

  2. Dilation of blood vessels:

    • Alcohol (to excess, of course).
    • Antidepressants, e. g. amitryptiline.
    • Vasodilator drugs (Ca channel blockers, ACE inhibitors, Angiotensin II receptor blockers).
    • Nitrates (nitroglycerine is one).
    • Bacterial infections (some). These readily cause shock.
    • Exposure to heat.
    • Nerve damage (Diabetes mellitus and others).

  3. Decrease in blood volume:

    • Diarrhea (various causes).
    • Diuretics.
    • Bleeding (rather obvious).
    • Excessive sweating.
    • Excessive urination (Diabetes m. and insipidus, Addison’s Disease).

  4. Inhibition of the brain centers:

    • Alcohol.
    • Antidepressants.
    • Antihypertensive drugs --methyldopa and clonidine.
    • Barbiturates.

  5. Impairment of the Autonomic Nervous System:

    • Amyloidosis.
    • Diabetes mellitus.
    • Parkinson’s Disease.
    • Other nervous system disorders.

Doctor’s Practical Guide:

Those who are concerned about causes of low blood pressure are usually people who are having symptoms popularly associated with low blood pressure. These might be fatigue, dizziness, lack of energy, lightheadedness, loss of balance, etc. Although these symptoms may very well be from low blood pressure they would not be expected to occur alone but in association with the symptoms of the disease causing the low blood pressure.

In other words, these symptoms are much more likely to be caused by diseases other than low blood pressure.

As I have said before (and it bears repeating) if you are having symptoms of any kind do not try to diagnose yourself. Instead see your doctor...it is difficult enough for us. See Symptoms of Low Blood Pressure

Fortunately, compared to high blood pressure, low blood pressure is relatively uncommon. It tends to be an end event. The vast majority of us running around all day in reasonably good health have no worries about low blood pressure. Most people are concerned about their blood pressure being high, not low. As well they should be.

A further thought: As mentioned frequently on this website about one in four people whose blood pressure is measured as high by someone else actually has a false elevation by an average of 27 mm. Could you not actually have low blood pressure and yet when measured by someone else it falsely reads as normal?

Note: This false elevation probably doesn’t occur in the hospital patient. See Cause of High Blood Pressure

The only way to really know your true blood pressure is to take it yourself. It’s easy to learn and very rewarding. See How To Take Blood Pressure and also How To Take Blood Pressure Booklet

Final thought: Please be aware that the above listed causes of low blood pressure may cause low blood pressure or may just contribute to it. Lots of people drink some alcohol or have some diabetes mellitus or take some of the drugs and have no problem. Shucks, otherwise, most of us would be dizzy or fainting all over the place.


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