Low blood pressure symptoms: dizziness, fainting and when to get help
Low blood pressure often shows up as dizziness, light-headedness or a near faint when you stand up. It is not always a problem, but it deserves attention when it causes symptoms or comes on suddenly. This guide explains the common signs, the everyday causes, how low blood pressure differs from high blood pressure, and the situations where you should get medical help straight away.
Key takeaways
- A reading below about 90/60 mmHg is commonly described as low, but what matters most is how you feel.
- Dizziness, light-headedness, blurred vision and fainting are typical symptoms.
- Dehydration, some medicines and standing up too quickly are common causes.
- Fainting with chest pain, confusion, a racing heart or after an injury is an emergency.
- Tell your GP about repeated symptoms, and never stop prescribed medicine without advice.
What is low blood pressure?
Low blood pressure, also called hypotension, is a reading that is lower than usual for you. A figure below about 90/60 mmHg is commonly cited as low, although there is no single cut-off that suits everyone.
Some people naturally run low and feel perfectly well. Fit, active people often have lower readings, and a low number with no symptoms is usually not a worry.
The key question is how you feel. If a low reading comes with dizziness, fainting or unusual tiredness, it is worth speaking to your GP, because your body may not be getting the blood flow it needs at that moment.
What are the symptoms of low blood pressure?
The most common sign is a wave of dizziness or light-headedness, especially when you stand up from a chair or bed. Symptoms often pass within a minute or two once you sit or lie down.
Other signs people describe include:
- Blurred or tunnel vision for a moment
- Feeling weak or unusually tired
- Nausea
- Cold, clammy or pale skin
- Difficulty concentrating
- Fainting or nearly fainting
Symptoms that come on suddenly, or that arrive with chest pain, confusion or breathlessness, need urgent medical attention. See the emergency section below.
What causes low blood pressure?
Several everyday and medical factors can lower blood pressure. In general terms, the common ones are:
- Dehydration from too little water, hot weather, vomiting, diarrhoea or heavy sweating
- Standing up too quickly, which lets blood pool in the legs for a moment
- Some medicines, including certain blood-pressure tablets, water tablets and some other prescriptions
- Long periods of standing in the heat, such as at a taxi rank or a queue
- Large meals, which can draw blood to the digestive system
- Blood loss, infection or other illness
- Pregnancy, heart rhythm problems and hormonal conditions
Is low blood pressure the opposite of high blood pressure?
In numbers, yes, but the experience is very different. High blood pressure usually causes no symptoms at all, which is why regular checks matter. Low blood pressure is the one that is more likely to make you feel unwell on the spot.
Neither is simply good or bad. A reading is judged against your normal, your symptoms and your health history. Our guide to normal blood pressure readings explains the usual ranges, and the guide on symptoms of high blood pressure shows how the other end looks.
If you take medicine for high blood pressure and start to feel dizzy, do not stop or change the dose on your own. Speak to your GP or pharmacist, who can check whether the dose still suits you.
What should I do when I feel dizzy or faint?
Sit or lie down straight away. If you lie down, raise your legs a little above heart level, which helps blood flow back to the head. This simple step also stops you from falling and hurting yourself.
Once you feel steadier, drink a glass of water and rise slowly, pausing on the edge of the bed or chair first. Avoid driving, climbing ladders or using machinery until you feel completely well.
A few daily habits help some people: drinking enough fluids through the day, getting up slowly, not standing still for long periods in the heat, and eating smaller, more regular meals. Ask your GP before adding extra salt, as that suits some people and not others.
When is low blood pressure an emergency?
Get emergency help, by going to the nearest emergency unit or calling an ambulance, if low blood pressure symptoms come with any of the following:
- Fainting with chest pain, a racing or very irregular heartbeat, or shortness of breath
- Confusion, difficulty speaking or weakness on one side of the body
- Cold, clammy, pale skin with fast, shallow breathing
- Heavy bleeding, a serious injury or a fall with a head knock
- High fever, vomiting or diarrhoea that will not stop, or black stools
- A faint that lasts more than a minute or happens more than once
Lay them flat on their back, raise their legs, loosen tight clothing and check that they are breathing. If they do not wake quickly or are not breathing normally, call for emergency help immediately.
When should I see my GP about low blood pressure?
Book a visit if dizziness or fainting happens more than once, if it limits your daily life, or if you notice it after starting a new medicine. Bring a list of everything you take, including supplements, and a short log of when symptoms happen and what you were doing.
Your GP may check your blood pressure lying and standing, ask about fluids and medicines, and arrange tests if needed. Our guide on choosing a home monitor explains how to build a reading log you can bring along.
Older adults deserve extra care, because falls can cause serious injury. If a parent or grandparent often feels dizzy on standing, encourage a check-up.
Frequently asked questions
What blood pressure reading is considered low?
A reading below about 90/60 mmHg is commonly cited as low. What matters most is whether you have symptoms and what is normal for you, so your GP interprets the number alongside how you feel.
Why do I get dizzy when I stand up quickly?
When you stand, blood moves toward your legs and your body needs a moment to adjust. If it adjusts slowly, you feel light-headed for a few seconds. Standing up gradually and staying hydrated usually helps. See your GP if it happens often.
Can dehydration cause low blood pressure?
Yes. Losing fluid through heat, sweating, vomiting or diarrhoea reduces the volume of blood in your body, which can lower blood pressure. Sip water regularly, especially in hot weather.
Can my blood-pressure tablets make me dizzy?
Some medicines can lower pressure more than needed in certain people. Do not stop your tablets yourself. Tell your GP or pharmacist about the dizziness so they can check your dose.
Is low blood pressure dangerous?
Often it is harmless, especially if it causes no symptoms. It can become a concern when it causes fainting, falls or comes with other warning signs such as chest pain or confusion.
Should I add more salt if my blood pressure is low?
That advice suits some people and not others. Ask your GP before changing your salt intake, especially if you have a heart, kidney or high blood pressure history.
Can I have low and high blood pressure at different times?
Yes. Blood pressure changes through the day and can be affected by medicines, meals, heat and posture. A log of readings helps your GP see the pattern.