Low blood pressure (hypotension)
Your health expert: Professor Mark Westwood, Consultant Cardiologist
Content editor review by Victoria Goldman, Freelance Health Editor, June 2023
Next review due June 2026
Low blood pressure (hypotension) is when your blood pressure falls much lower than is normal for you. When this happens, low blood pressure symptoms may include dizziness and fainting.
Having your blood pressure taken
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About low blood pressure
Your blood pressure is a measure of the force that your blood puts on the walls of your arteries as it’s pumped around your body. You’ll see your blood pressure shown as two numbers, such as 120/80mmHg. The letters mmHg stand for millimetres of mercury, which is the unit used to measure blood pressure.
- The first number is the highest pressure when your heart contracts – this is your systolic blood pressure.
- The second number is the pressure when your heart is fully relaxed – this is your diastolic blood pressure. .
There’s no set level at which your blood pressure is said to be too low – it’s different for everyone. You may have a blood pressure that’s naturally lower than average – but if it doesn’t cause you any problems, it won’t be classed as ‘low blood pressure’. Your blood pressure is usually only considered to be too low if it’s causing symptoms.
High blood pressure is a risk to your health – it can lead to serious conditions, such as stroke, coronary heart disease and kidney failure. The lower your blood pressure, the less likely you are to have these problems. But if your blood pressure gets much lower than usual for you, it can cause fainting, falls and accidents. See our Symptoms of lower blood pressure section for more information.
Causes of low blood pressure
Lots of things can make your blood pressure drop lower than normal. These include the following.
- Loss of fluid – for example, from losing a lot of blood, severe vomiting and diarrhoea, or sweating a lot due to vigorous exercise.
- Problems with your heart, which means it can’t pump as much blood around your body.
- Diseases that affect your autonomic nervous system, which normally regulates your blood pressure – including Parkinson’s disease and both type 1 and type 2diabetes.
- Side-effects of some medicines, including some for high blood pressure, heart disease and depression.
- Severe infection, or a severe allergic reaction.
- Reflex syncope – some things can cause a quick but temporary drop in your blood pressure, making you to lose consciousness (faint) briefly. These can include standing for a long time, pain, emotional stress and fear.
- Pregnancy – a drop in blood pressure can be part of the normal changes that happen to your body. See our Pregnancy and low blood pressure section for more information.
Sometimes, your blood pressure only drops when you stand up. This causes blood to pool in your legs. This is called postural or orthostatic hypotension and can be triggered by the factors listed above. But it’s also more common in older people. This is because the systems in your body that normally regulate your blood pressure may not work so well as you get older.
You may get postural hypotension after eating a meal, especially one high in carbohydrates. This is called postprandial hypotension.
Pregnancy and low blood pressure
It’s normal for your blood pressure to get lower during pregnancy. This is mainly because your hormones relax the walls of your blood vessels. Your blood pressure may fall very early in your pregnancy and reach its lowest point during your second trimester (weeks 13 to 28). It then starts to rise again, returning to normal after you have your baby.
If you have low blood pressure during pregnancy, you may feel faint and dizzy suddenly when you get up from lying or sitting down. This is called postural hypotension. You can help relieve your symptoms by making sure you get up slowly from lying or sitting. And if you feel you’re going to faint, sit or lie down right away.
If you lie flat on your back in late pregnancy, your uterus can press down on a large vein that carries blood to your heart from other parts of your body. This can cause low blood pressure and make you feel faint. So you should lie on your side in late pregnancy instead.
Occasionally, symptoms of low blood pressure may be caused by other underlying health conditions affecting your pregnancy. Always tell your midwife about your symptoms. Seek medical help if you have dizziness or fainting or any other symptom that you’re worried about.
Symptoms of low blood pressure
If your blood pressure is naturally quite low, you’re unlikely to have any symptoms and it's not something to worry about.
However, if your blood pressure becomes lower than usual for you, it can cause symptoms such as:
- dizziness or light-headedness
- fainting
- palpitations (you can feel your heart beating more forcefully)
- feeling sick
- blurred vision
- feeling tired or weak
You might only have these symptoms when you stand up from sitting or lying down, (postural or orthostatic hypotension). This might even make you fall over.
If you keep having symptoms like these, contact your GP.
If your blood pressure drops very quickly or suddenly, for instance, if you’ve lost a lot of blood, this can lead to shock. This is an emergency situation: you’ll feel and look very unwell and will need to call for medical help straightaway.
Diagnosis of low blood pressure
Your GP will ask about your symptoms and examine you. They’ll measure your blood pressure using either an automated digital device or a manual device. To find out more about how blood pressure is measured, see our animation at the top of this page – Having your blood pressure taken.
If you have symptoms of postural hypotension (low blood pressure when you stand up), your GP may also measure the change in your blood pressure while you’re sitting (or lying) and then standing. If your blood pressure is much lower when you stand up than when you’re sitting down, this suggests you have postural hypotension.
Your GP may also recommend that you have:
- some blood tests to check your general health
- an electrocardiogram (ECG)to check the electrical activity of your heart
- an echocardiogram (ultrasound of your heart) if they need to check for any underlying problems affecting your heart
If your symptoms need further investigation, your doctor may recommend you have a tilt test. In a tilt test, you lie on a table that’s gradually tilted until it’s nearly upright. Your blood pressure and heart rhythm and rate are monitored while the table is tilting. You’ll only be in the tilted position for between 15 and 45 minutes.
Your GP may refer you to a cardiologist (doctor specialising in heart problems) if they can’t find out what’s causing your low blood pressure – or if they think you may have a problem with your heart.
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Self-help for low blood pressure
If you have low blood pressure, you can take simple steps to help prevent or reduce your symptoms.
If you have postural hypotension (get symptoms when you stand up), the following may help.
- Stand up slowly from sitting or lying down, especially when you first wake up. If you’re lying down, sit for a while first before standing.
- Take care getting out of hot baths or showers. It may be best to avoid very hot baths.
- Make sure you drink enough fluid to keep hydrated.
- If you drink alcohol, don’t drink to excess.
- If you can, try raising the head of your bed a little.
- When you stand up, it may help to cross your legs, stand on tiptoes or tense your muscles.
- Try to keep physically active.
If you get symptoms after eating:
- eat smaller, more frequent meals
- choose foods that don’t contain too much carbohydrate (such as rice, bread and pasta)
- avoid standing suddenly after a meal
If you’re fainting because of low blood pressure, it can help to think about any possible triggers and whether you can avoid or manage them. This may include not standing still for long periods or avoiding warm environments.
If you feel faint, you should immediately sit or lie down if you can do so safely. Put your feet up so that they’re higher than the level of your heart. If you can’t sit or lie down, it may help if you can:
- squat down
- cross your legs
- tense the muscles in your legs and arms
If your symptoms don’t go away, seek medical attention.
Treatment for low blood pressure
Low blood pressure treatment aims to increase your blood pressure so you don’t get any symptoms and won’t be at risk of falling over.
Your GP will go through some simple things you can do to help yourself – see our Self-help for low blood pressure section for more information. They may also suggest you:
- increase the salt in your diet. Don’t do this unless your doctor suggests it, as it may affect other health conditions you have
- wear compression stockings if you have postural hypotension (low blood pressure when you stand up). These can help stop blood from pooling in your legs
Medicines
Sometimes, low blood pressure can be caused by medicines you’re taking, including those for high blood pressure. Your GP may review your medicines to see if any of these could be causing your low blood pressure or making your symptoms worse. They may suggest you stop or change your medicines to see if this helps. But don’t stop or change any of your medicines without discussing it with your GP first.
Doctors don’t usually prescribe medicines to treat low blood pressure as these can cause side-effects. But your GP or a specialist may prescribe medicines if self-help measures don’t stop your symptoms of low blood pressure. This may include medicines that:
- control the amount of salts and fluids in your body
- make your veins constrict (get smaller), increasing your blood pressure
You may need treatment for any underlying health condition that’s causing your low blood pressure. If so, your GP will discuss with you what’s best for you.
Low blood pressure is when your blood pressure falls much lower than is normal for you. This can cause symptoms such as dizziness and fainting. For more information, see our about low blood pressure section.
Low blood pressure has lots of causes. These include sweating a lot, a problem with your heart or nervous system, or side-effects of medicines you’re taking. For more information, see our causes of low blood pressure section.
Diabetes can damage the nerves in your legs. If this happens, blood may pool in your legs when you stand up. Your blood pressure then falls. This is called postural hypotension. For more information, see our causes of low blood pressure section.
The lower your blood pressure, generally the better – as long as it’s not causing problems. But low blood pressure can be a sign of a heart problem or lead to fainting, falls or accidents. See our about blood pressure section.
You can usually treat low blood pressure with self-help measures, such as eating regularly. Doctors sometimes prescribe medicines to increase blood pressure. For more information, see our treatment of low blood pressure section.
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