What is low blood pressure (hypotension)?

Low blood pressure, or hypotension, is generally a reading below 90/60 mmHg, according to the NHS. For many people it causes no problems at all and needs no treatment. It becomes worth attention when it brings symptoms such as dizziness or fainting, or when it drops suddenly, because that can mean your organs are not getting enough blood.

Most of the focus in blood pressure health is on numbers that are too high, so low readings can be confusing. This guide explains what counts as low blood pressure, the symptoms and causes to know, and the signs that mean you should get help.

What counts as low blood pressure?

Blood pressure is written as two numbers measured in millimetres of mercury (mmHg): the systolic (top) pressure when your heart beats, and the diastolic (bottom) pressure when it rests between beats. The NHS describes low blood pressure as a reading below 90/60 mmHg.

Unlike high blood pressure, there is no single cut-off that makes low blood pressure a problem. Mayo Clinic notes that what matters is whether the low reading comes with symptoms. Plenty of healthy people, especially those who are fit or naturally run low, sit below 90/60 and feel completely well. In that case it is usually nothing to worry about. For a closer look at a specific low-normal result, see what a reading of 90/60 means.

Symptoms of low blood pressure

When blood pressure drops too low for your body, less blood reaches the brain and other organs, which can cause:

• dizziness or lightheadedness
• feeling faint or actually fainting
• blurred vision
• nausea
• unusual tiredness
• trouble concentrating

The NHS notes these symptoms often appear at particular moments, such as when you stand up quickly, after a meal, or when you are dehydrated. If you only feel them briefly and occasionally, it may simply be a sign to slow down and rehydrate. If they are frequent or severe, it is worth seeing your doctor.

What causes low blood pressure?

Hypotension has many possible causes, and often more than one is involved. Mayo Clinic and the NHS point to:

• Dehydration, which reduces blood volume and is one of the most common triggers.
• Medications, including diuretics, some antidepressants, and treatments for high blood pressure such as beta blockers and alpha blockers.
• Pregnancy, as blood pressure often dips in the early and middle stages.
• Heart problems, such as a very slow heart rate or heart valve issues.
• Hormonal conditions, including thyroid problems and adrenal insufficiency.
• Prolonged bed rest or standing for long periods.
• Severe causes, such as major blood loss, a serious infection, or a severe allergic reaction, which can drop blood pressure dangerously.

A few specific patterns have their own names. Orthostatic (postural) hypotension is a drop that happens when you stand up. Postprandial hypotension is a drop after eating. Both are more common in older adults, according to Mayo Clinic.

How low blood pressure is managed

If your low blood pressure causes no symptoms, the NHS notes it usually needs no treatment. When symptoms do appear, the approach depends on the cause. Simple steps often help: drinking more water, standing up slowly, eating smaller meals, and, if a medicine is responsible, reviewing it with your doctor. The NHS notes that for some people a doctor may suggest increasing fluids, adjusting salt intake, or wearing compression stockings, depending on the cause. Your doctor will look for and treat any underlying condition rather than the number alone.

Because readings move through the day, the most useful thing you can do is keep a record. Measuring at consistent times and noting when symptoms strike gives your doctor a much clearer picture than a single reading. Our guides on how to measure blood pressure at home and what counts as normal blood pressure can help you put a low reading in context.

When to see a doctor

See your doctor if you often feel dizzy, faint, tired, or unwell alongside low readings, or if your blood pressure has dropped noticeably without an obvious reason. These are worth investigating even when they seem mild.

Call emergency services right away if someone shows signs of shock from a sudden, severe drop in blood pressure. The NHS lists these warning signs:

• confusion, especially in older people
• cold, clammy, pale skin
• rapid, shallow breathing
• a weak and rapid pulse
• fainting or loss of consciousness

A sudden severe drop is a medical emergency, as it can starve the organs of blood. When in doubt, seek help rather than wait.

Frequently asked questions

Is low blood pressure dangerous?

Often it is not. The NHS notes that low blood pressure without symptoms usually needs no treatment. It becomes dangerous when it drops suddenly or brings symptoms like fainting, confusion, or signs of shock, which need urgent care.

What is considered low blood pressure?

The NHS describes low blood pressure as a reading below 90/60 mmHg. There is no strict danger threshold, though, because what matters most is whether the low reading causes symptoms.

Can dehydration cause low blood pressure?

Yes. Dehydration reduces the volume of blood in your body, which can lower blood pressure and cause dizziness or fatigue, according to Mayo Clinic. Rehydrating often helps, but persistent symptoms should be checked by a doctor.

Why do I feel dizzy when I stand up?

A brief drop in blood pressure on standing is called orthostatic (postural) hypotension. Standing up slowly usually helps. If it happens often or causes fainting, see your doctor, since Mayo Clinic notes it is more common with age and some medications.

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This is educational information, not medical advice. If you have questions about your blood pressure or take medication for it, speak with your doctor. For guidance, see the NHS or Mayo Clinic. In an emergency, call your local emergency number.

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Last reviewed: October 2026