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What is low blood pressure?

 

Low blood pressure, also known as hypotension, is when you have a blood pressure level that is below the normal range.

If your blood pressure is naturally low, this probably won’t cause you any problems and won’t need treating. In fact, the lower your blood pressure, the lower your risk of heart disease and stroke.

Low blood pressure can sometimes be caused by medications or can be a sign of another health problem. This can sometimes cause problems such as falls, fainting and feeling dizzy, so it might need looking into and treating. Speak to your doctor or nurse if you’re worried about low blood pressure.

 

What are the symptoms of low blood pressure?

Low blood pressure often has no symptoms, but can sometimes mean that not enough blood is flowing to your brain or organs. This can cause symptoms such as:

  • feeling dizzy, faint or light-headed
  • feeling unsteady
  • feeling sick (nausea)
  • blurred vision
  • a general feeling of weakness
  • feeling confused
  • suddenly noticing your heartbeat (palpitations)
  • fainting

If you have these symptoms, stop what you’re doing and sit down or lie down in case you fall, and drink some water.

Speak to your doctor or nurse if you experience these symptoms. As well as being unpleasant, they could mean you’re at risk of having a fall. They could also be a sign of another health problem.

 

Low blood pressure when you stand up


Sometimes, changes in your posture can cause your blood pressure to drop, for example, going from sitting or lying down to standing up. You might feel the symptoms listed above when you stand up, such as feeling dizzy or faint. They will pass quickly as your body adjusts, but can put you at risk of falls.

This is called postural hypotension or orthostatic hypotension. It’s caused by changes to your arteries which happen as you get older and if you’re taking medications to lower your blood pressure. 

 

What causes low blood pressure?


Some people have a blood pressure level that is naturally low. That is, there is no specific cause or reason why. It can be the result of a healthy lifestyle and being fit and active, and your genes may play a role.

Your blood pressure varies throughout the day. It might drop when you’ve just eaten while your blood is carried to your gut, if you’ve been standing up for a long time, if you’re dehydrated, and if the temperature is warm.

There are a number of other possible causes of low blood pressure:

Medications
Low blood pressure, and low blood pressure when you stand up, can be caused by medications. These include medications to lower blood pressure, antidepressants and beta blockers, which are used to treat heart problems. 

Health problems
Low blood pressure can also be caused by an illness or health problem.

  • Diabetes can affect the normal control of blood pressure because it can affect your hormones and the nerves leading to your blood vessels. If the nerves are affected your blood pressure might drop when you stand up because your blood vessels can’t adjust to the new position quickly enough.
  • Neurological conditions (conditions which affect the nervous system).    For example, Parkinson’s disease. These can affect the autonomic nervous system which controls the things our body does without us thinking, including the widening and narrowing of the blood vessels. If your blood vessels are wider, your blood has more space to flow through so your blood pressure falls. The drugs that are prescribed to treat Parkinson’s can also cause low blood pressure, particularly postural hypotension.
  • Problems with your adrenal glands. For example, Addison’s disease, an infection, or a tumour. The adrenal glands sit just above your kidneys and produce hormones which help to control your blood pressure. If they are damaged, this can cause a drop in these hormones and a drop in your blood pressure.
  • Neurally-mediated hypotension.  This is when you have been standing up for a long time and your body sends signals to your brain telling it that your blood pressure is high, when in fact it’s too low. Your brain then signals to your heart to slow down, and your blood pressure falls lower.
  • Heart problems.  Heart problems such as heart failure or hearts attack can lead to low blood pressure as the heart can’t pump blood around the body as well as it should.
  • Anaemia. This is where your red blood cell count is lower than normal, or the amount of haemoglobin – the part of the blood that carries oxygen – is lower than normal.
  • Serious injury and shock. Serious injury, burns, and going into shock can all cause your blood pressure to drop. For example, if you lose a lot of blood if you have an allergic reaction called anaphylactic shock, or if you have shock caused by a bacterial infection.

 

How is low blood pressure diagnosed?


Like high blood pressure, low blood pressure (hypotension) can be diagnosed easily with a blood pressure check.

If you feel dizzy or faint when you stand up, you might need to have your blood pressure measured when you’re lying down and again while you are standing up.

You might be offered a tilt table test. This is where you lie on a table that starts in a horizontal position, then slowly tilts so that you’re in an almost upright position – as if you were standing. You will have your blood pressure and pulse monitored, and any symptoms you feel will be recorded. You might also have a blood test to check the levels of certain hormones.

 

What is a low blood pressure reading?


A blood pressure reading below 90/60mmHg is considered low blood pressure. Only one of the numbers needs to be at this level or lower to count as low blood pressure. Read more about what the numbers mean.

 

How is low blood pressure treated?


If your blood pressure is naturally low and isn’t causing you any problems it probably won’t need any treatment. If you have symptoms and your doctor or nurse feels that you would benefit from treatment, they will try to find the cause of your low blood pressure so that they can find the best way to treat it. 

The treatments will vary depending on the cause.

  • A change in medications. If your GP thinks that your blood pressure is caused by a medication you’re taking they might want to try an alternative medication or a different dose.
  • Hormone replacement. If your low blood pressure is caused by a change in certain hormones, for example if your adrenal glands have been damaged, you may be referred to a specialist called an endocrinologist. They might prescribe hormone replacement medication.
  • Medicines to stimulate your nerves. If you have a neurological condition, you may be given medicines to stimulate the nerves.
  • Medicines for low blood pressure. These medicines narrow your blood vessels or expand the volume of your blood to raise your blood pressure. These are very rarely needed, as the treatments listed above and the changes you can make for yourself are usually enough.

 

What can I do for myself?


There are other things you can do for yourself to help with your symptoms.

  • Wear supportive elastic stockings (compression stockings). They put extra pressure on your legs which helps to improve circulation and raise your blood pressure. For some people this can be enough, but speak to your GP first because they aren’t suitable for everyone.
  • Stand up slowly from sitting or lying down. You can try other simple movements to get the blood flowing before you stand up, such as straightening and bending your legs.
  • Avoid standing for long periods of time. 
  • Drink enough water throughout the day, around 2 litres, so you don’t get dehydrated.
  • Eat little and often throughout the day. This avoids low blood pressure after eating. 

Read more
Read more about how blood pressure works.

 

 

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