If you have low blood pressure (hypotension), this means that it’s lower than would usually be expected for you and may cause symptoms such as fainting. It's usually good for your health to have as low a blood pressure as possible. However, when it becomes too low it can reduce the blood flow to your vital organs.
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. This is affected by the strength with which your heart pumps, and the size and flexibility of your arteries that carry the blood. Your blood pressure changes throughout the day. It’s lower when you sleep and rises when you wake up.
Blood pressure is expressed as two numbers, such as 120/80mmHg (millimetres of mercury). The first number shows the maximum pressure when your heart contracts – this is your systolic blood pressure. The second number shows the minimum pressure as your heart relaxes – this is your diastolic blood pressure.
If your blood pressure is too high (hypertension), you will be at greater risk of certain diseases, such as coronary heart disease and stroke. It's usually good to have low blood pressure, as this can reduce your risk of getting these conditions. The ideal blood pressure for adults is between 90/60 and 120/80mmHg.
There’s no recognised level for low blood pressure. If your systolic blood pressure is lower than 90, your GP may consider it to be low. However, blood pressure below this may be normal for some people, whereas others may develop symptoms of low blood pressure at a level above this. It also depends on other factors. For example, blood pressure is lower in pregnant women, particularly during the middle part of pregnancy. Low blood pressure problems are also more common as you get older. Low blood pressure is only considered to be a problem if you’re having symptoms.
If your blood pressure falls below what is usual for you, it may result in not enough blood being pumped around your body. This may mean that the supply of oxygen to your organs, including your brain, is restricted. This can lead to symptoms such as fainting.
If your blood pressure is naturally low, you’re unlikely to have any symptoms and it's not something you should be concerned about.
However, if your blood pressure becomes lower than usual for you, it can cause symptoms such as:
You may find that you mainly get these symptoms when you stand up from a sitting position or from lying down. This usually happens within the first few seconds or minutes. This is called postural (orthostatic) hypotension. If you tend to get symptoms after eating a meal, it's called postprandial hypotension.
Seek medical advice as soon as possible if you have any of the symptoms of low blood pressure.
If your blood pressure has been described as low but you don't have any symptoms, there‘s unlikely to be any underlying problem. It means that this is a healthy blood pressure for you.
It’s not uncommon to get an occasional sudden, temporary drop in blood pressure that causes symptoms, such as fainting. The medical term for this is syncope. Around half of us will get this at some point in our lifetime. A number of things can cause this, for example:
If you have low blood pressure that is regularly causing symptoms, the mechanisms that control blood pressure in your body might not be working properly. They are causing your blood pressure to drop.
If you have postural hypotension, your body doesn't respond quickly enough when you stand up, causing blood to stay in your legs. This means that less blood goes back to your heart so there isn’t as much for it to pump out, causing your blood pressure to fall. Postprandial hypotension happens when blood flows to your digestive system after you eat a meal. Your body doesn't respond in the usual way to maintain blood pressure in the rest of your body. Both of these conditions are more common in older people.
There may be an underlying condition that‘s causing your low blood pressure. Some examples include:
Your GP will ask about your symptoms and examine you. He or she will measure your blood pressure using a device called a sphygmomanometer. This is usually an automated, digital device, consisting of a monitor attached to a cuff, which is wrapped around your upper arm. Your GP will press a button to inflate the cuff, and then it will automatically slowly deflate. A sensor in the cuff detects your pulse when the cuff is fully inflated. As it deflates it converts this into a measurement of blood pressure. The result is shown on the display screen. Your GP may decide to use a manual device instead. However, they both do the same job.
If you have symptoms of postural hypotension, your GP may also measure the change in your blood pressure while you’re sitting (or lying) and then standing. If it’s much lower when you stand up compared with when you’re sitting down, this suggests you have postural hypotension.
You might need to have a test called a ‘tilt test’ to understand what’s causing your symptoms. This usually happens in hospital. It involves being slowly tilted from lying down to an upright position on a table as your blood pressure, heart rate and rhythm are monitored. See our FAQ for more information.
You’re unlikely to need any treatment if your blood pressure is naturally low and you don't have any symptoms. If you have symptoms, your treatment will depend on the cause of your low blood pressure. For example, if you’re taking water tablets (diuretics) and are causing your blood pressure to drop, your GP may suggest stopping or changing your medication. Your doctor will review any medicine you’re taking that could be making it worse or bringing it on.
During your pregnancy, you will regularly have your blood pressure checked at your antenatal appointments. This is so any problems can be picked up. If you’re feeling dizzy or worrying about it, speak to your midwife.
There are several self-help measures that can help if you have either type of hypotension.
If you have postural hypotension, your GP may suggest some actions you can take which might help. These are listed below.
Your GP may advise you to alter your diet so it includes more salt. However, don't do this unless your GP advises you to as it needs to be done in a controlled way.
If you have postprandial hypotension, your GP may make the following suggestions.
These measures may not be suitable for everyone. Ask your GP about what’s right for you.
Occasionally, your GP or a specialist may prescribe medicines if self-help measures don’t stop your symptoms of low blood pressure. These may include medicines that:
Your GP may refer you to a specialist for further tests before prescribing these medicines, or if they are not helping.
Reviewed by Natalie Heaton, Bupa Health Information Team, June 2014.
For answers to frequently asked questions on this topic, see FAQs.
For sources and links to further information, see Resources.
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This information was published by Bupa's Health Information Team and is based on reputable sources of medical evidence. It has been reviewed by appropriate medical or clinical professionals. Photos are only for illustrative purposes and do not reflect every presentation of a condition. The content is intended only for general information and does not replace the need for personal advice from a qualified health professional. For more details on how we produce our content and its sources, visit the about our health information page.
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