Low Blood Pressure (Hypotension): Symptoms, Causes, Home Care and When It Is Dangerous

High blood pressure gets most of the attention, but low blood pressure (hypotension) can cause dizziness, falls and fainting, and sometimes signals a serious problem. A blood pressure below 90/60 mmHg is generally considered low, although what matters is how you feel. Many healthy people live perfectly well with readings of 95/60 or lower.

Symptoms

• Dizziness or light-headedness, especially on standing
• Fainting or near-fainting
• Blurred or dimming vision
• Weakness and fatigue
• Nausea
• Difficulty concentrating
• Pale, cold, clammy skin
• Rapid, shallow breathing

If you have no symptoms, a low reading is usually not a worry.

Types of low blood pressure

• Orthostatic (postural) hypotension: a drop of 20 mmHg systolic or 10 mmHg diastolic within three minutes of standing up. Common in older adults and after prolonged bed rest.
• Post-meal hypotension: pressure falls 1-2 hours after eating, mainly in older people.
• Neurally mediated hypotension: a drop after standing for a long time or emotional stress, more common in young people.
• Severe hypotension linked to shock: a dangerously low pressure from infection, bleeding, heart failure or allergy. This is an emergency.

Common causes

• Dehydration from fever, vomiting, diarrhoea, sweating, hot weather or not drinking enough, which is common in dengue and gastroenteritis
• Blood pressure and heart medicines, diuretics, beta-blockers, alpha-blockers, nitrates, some antidepressants and Parkinson's drugs
• Heart problems: slow heart rate, valve problems, heart failure
• Endocrine problems: under-active thyroid, adrenal insufficiency, low blood sugar, diabetes complications
• Blood loss or anaemia
• Severe infection (sepsis) or allergic reaction
• Pregnancy, especially in the first and second trimesters
• Nutritional deficiencies: low iron, vitamin B12 or folate
• Nerve problems from diabetes or Parkinson's disease
• Alcohol

Is it dangerous?

Low blood pressure is dangerous when the brain, heart and kidneys do not receive enough blood. Falls from fainting can cause fractures and head injuries, especially in older adults. Seek emergency help if low pressure comes with:

• Chest pain, breathlessness or a very fast or slow pulse
• Confusion, drowsiness or difficulty waking
• Cold, clammy, pale or bluish skin
• Fever, severe infection or signs of dengue shock (see dengue warning signs)
• Black stools, vomiting blood or heavy bleeding
• Fainting with injury, or loss of consciousness

What to do at home if you feel faint

1. Sit or lie down straight away, with your legs raised above heart level.
2. Drink water or oral rehydration solution.
3. Rest until symptoms settle, and rise slowly.
4. Check your blood pressure if you have a monitor. See how to check blood pressure at home.
5. If you have just taken a new medicine, contact your doctor.

Prevention and day-to-day tips

• Get up slowly: sit on the bed edge for a minute before standing.
• Drink enough fluids, aiming for pale yellow urine. Our water intake calculator gives a guide.
• Eat small, frequent meals, and limit large carbohydrate-rich meals if you feel faint afterward.
• Avoid alcohol and standing still for long, and avoid very hot showers.
• Cross your legs or tense your leg muscles when you must stand.
• Wear compression stockings if your doctor recommends them.
• Do not stop prescribed medicines on your own. Ask your doctor to review doses.
• Add salt only if your doctor has advised it, as extra salt is harmful for people with high blood pressure, heart or kidney disease.

Diagnosis

Your doctor will measure lying and standing blood pressure, review medicines and may order blood tests (blood count, sugar, thyroid, cortisol, kidney function), an ECG, echocardiogram or tilt-table test. Treatment targets the cause, such as treating dehydration, stopping or reducing a medicine, correcting anaemia or treating the heart condition.

Medicines for persistent low blood pressure

Some people with severe orthostatic hypotension are prescribed medicines such as fludrocortisone or midodrine. These need specialist supervision because they can cause high blood pressure when lying down.

Low blood pressure in pregnancy and older adults

Mild low blood pressure is common in early pregnancy and usually improves later. Older adults are more prone to falls, so they should have a medicine review and a home safety check.

When to see a doctor

See a doctor if you have repeated dizziness, fainting, falls, or readings below 90/60 with symptoms, or if low pressure starts after a new medicine. Go to emergency for the warning signs above. For comparison, read about high blood pressure.

References

• NHS: low blood pressure (hypotension)
• American Heart Association: low blood pressure, when blood pressure is too low
• European Society of Cardiology: guidelines for the diagnosis and management of syncope
• Consensus statement on the definition of orthostatic hypotension, Clinical Autonomic Research