Low blood pressure (hypotension): symptoms, causes and what to do

Most people with low blood pressure have no noticeable symptoms. NHS inform and the British Heart Foundation (BHF) both say this. When symptoms occur it is because not enough blood is reaching the brain or organs, according to Blood Pressure UK.

The NHS says to get your blood pressure checked if you keep getting symptoms such as the ones listed below. If they happen when you stand up or suddenly change position, you may have postural hypotension.

Blood Pressure UK advises that if you have these symptoms you should stop what you are doing and sit or lie down in case you fall, and drink some water, then speak to your doctor or nurse because the symptoms put you at risk of falls and could be a sign of another health problem.

• Lightheadedness or dizziness.

• Feeling sick (nausea).

• Blurred or fading vision.

• Generally feeling weak or tired.

• Confusion.

• Fainting.

• Suddenly noticing your heartbeat (palpitations), according to Blood Pressure UK.

Blood pressure is the pressure of blood in the arteries, the vessels that carry blood from the heart around the body. NHS inform says there needs to be a certain level of pressure in the arteries to move blood around.

The NHS defines low blood pressure as a reading of less than 90/60mmHg. The BHF stresses that this does not necessarily mean there is a problem, though you might need treatment if it is causing symptoms. Blood Pressure UK notes that a naturally low blood pressure can be the result of a healthy lifestyle, being fit and active, and your genes, and that the lower your blood pressure, the lower your risk of heart disease and stroke.

Blood pressure also varies through the day. NHS inform lists the time of day (it falls overnight), feeling relaxed, rest, cold temperatures and being fit and healthy as things that can contribute to a lower reading.

There are many possible causes. The NHS says it may be low because you are fit and healthy, or because you inherited it from your parents. Some people develop it as they get older. The table groups the causes named by the NHS, NHS inform, the BHF and Blood Pressure UK.

Sometimes blood pressure drops when posture changes, for example from sitting or lying to standing. Blood Pressure UK says this is called postural or orthostatic hypotension, that the dizziness or faintness passes quickly as the body adjusts but can put you at risk of falls, and that it is caused by changes to the arteries that happen with age and by taking medicines that lower blood pressure.

NHS inform adds that symptoms can also happen after eating, which is known as postprandial hypotension. Blood Pressure UK says blood pressure might drop after a meal while blood is carried to the gut.

If you feel dizzy when you stand, a doctor or nurse may measure your blood pressure lying down and again standing. Blood Pressure UK says you might also be offered a tilt table test, where you lie on a table that slowly tilts upright while your blood pressure and pulse are monitored, and a blood test to check hormone levels.

If you have symptoms, NHS inform says your healthcare professional will try to find out why so that they can help you manage the cause. The NHS says a GP may suggest changing medicines or altering the dose if that is the cause, or wearing support stockings, which can improve circulation and increase blood pressure.

The NHS says medicine to increase blood pressure is rarely needed because simple lifestyle measures or treating the underlying cause is usually effective. Blood Pressure UK describes the options when treatment is needed: a change of medicines, hormone replacement if damaged adrenal glands are the cause, medicines to stimulate the nerves, and, very rarely, medicines that narrow blood vessels or expand blood volume.

The BHF says that if low blood pressure is caused by something else it is treated by managing the cause, for example stopping bleeding after an injury or drinking more water if you are dehydrated. Do not stop or change prescribed medicines without speaking to your GP.

The NHS, NHS inform and the BHF give a consistent list. Speak to your doctor before making major changes to lifestyle, diet or exercise, particularly if you have a heart condition or a fluid restriction.

• Get up slowly from sitting or lying, and take care getting out of bed (NHS). NHS inform suggests standing up slowly, particularly first thing in the morning, and stretching before standing.

• Eat small, frequent meals rather than large ones; lying or sitting down for a while after eating may help (NHS and NHS inform).

• Increase the amount of water you drink. If you are on a daily fluid restriction because of a heart condition, check with your doctor first (NHS inform, BHF).

• Do not sit or stand for long periods, and do not change posture suddenly (NHS).

• Do not drink too much alcohol (NHS).

• Ask your doctor about adding more salt to your diet (BHF).

• Move regularly. The BHF suggests regular exercise and crossing and uncrossing your legs rather than staying still.

• Ask your doctor whether support stockings are suitable for you.

The NHS lists pregnancy among the causes of low blood pressure. The BHF explains that blood vessels can expand in the first stages of pregnancy, which causes blood pressure to drop, and that after giving birth blood pressure should go back to how it was before pregnancy.

NHS inform says to speak to your healthcare professional if you have symptoms such as dizziness, light-headedness or fainting, and that applies in pregnancy. After fainting, the NHS says that if a person is pregnant, especially after 28 weeks, it is better to lay them on their side.

The NHS says to see a GP if you keep getting symptoms of low blood pressure such as dizziness and fainting. It also says that if you have fainted you should get checked by a GP to find out what might have caused it, because fainting is not usually serious but it is important to rule out causes.

The NHS says to call 999 if someone who has fainted is not breathing, cannot be woken within 1 minute, has not fully recovered or has difficulty with speech or movement, has chest pain or a pounding, fluttering or irregular heartbeat, has seriously hurt themselves, is having a seizure, fainted while exercising or fainted while lying down. Do not drive yourself to A&E.

The BHF notes that losing a lot of blood from an injury or internal bleeding reduces blood volume and can cause a severe drop in blood pressure. The NHS also says you must tell the DVLA if you are fainting regularly because it could affect your ability to drive.

You can have your blood pressure checked by a pharmacist, practice nurse or GP, or measure it yourself at home with a home monitor, according to the NHS. The NHS adds that if you are aged 40 to 74 you should have your blood pressure checked at least once every 5 years as part of the NHS Health Check.

A GP can review your medicines and look for a cause, and Blood Pressure UK says you may be referred to a specialist such as an endocrinologist if hormones are involved. Private clinics offer the same assessments, including blood pressure monitoring and tilt testing, and results should still be shared with your GP.