There are a number of things that can cause low blood pressure. They include:
- the use of certain medications, such as anti-depressants, and medicines to treat high blood pressure,
- diabetes mellitus which can cause damage to the nerves that supply your blood vessels, resulting in a fall in blood pressure when you stand up (postural or orthostatic hypotension),
- serious injuries, such as burns, or those that cause severe blood loss, and lead to shock, and a reduction in blood volume,
- serious illnesses, or conditions, such as a heart attack, or adrenal gland failure,
- rare nerve conditions that affect the nerves in your legs can cause a severe drop in blood pressure when you stand up (postural or orthostatic hypotension),
- increasing age - as you get older, your arteries become stiffer which can cause your blood pressure to drop, particularly when you stand up, and
- pregnancy during the early to mid stages of pregnancy, low pressure is fairly common.
Blood pressure lowering medicines
Nowadays, most blood pressure lowering medicines do not cause a drop in blood pressure when you stand up. Alpha-blockers, such as doxazosin, are the only type of medicine that may cause a decrease in your standing blood pressure. You should have your standing blood pressure checked, if you are taking doxazosin, and you feel dizzy, or faint, when you stand up.
In the past, it was thought that low blood pressure could cause tiredness, depression, and anxiety. However, recent studies have found no strong evidence to suggest that low blood pressure causes these symptoms.
Adrenal gland failure
The adrenal glands are two small glands that are located just above your kidneys. They produce a number of hormones, including aldosterone, which controls the amount of salt in your body. If your adrenal glands become damaged, the production of aldosterone may be reduced, resulting in a loss of salt from your body. This can lead to low blood pressure, and may make you feel dizzy, or faint, if you stand up too quickly. Adrenal gland failure is rare but, if it is diagnosed, it can be treated by increasing the amount of aldosterone.
Serious illnesses
Sometimes, severe illnesses that cause infection, blood loss, or heart damage, may result in low blood pressure, particularly when sitting up or standing. If you have an acute illness, your blood pressure will be measured regularly because it is a good indicator of the severity of your illness.