Low blood pressure (hypotension): causes, symptoms and self-care

Blood pressure that is lower than usual is often harmless. This article explains what low blood pressure is, why it happens and what to do about it, using information from the NHS, MedlinePlus and the US National Heart, Lung, and Blood Institute (NHLBI).

1. Introduction

Blood pressure is the force of blood pushing against the walls of your arteries. It is written as two numbers. The top number (systolic) is the pressure when the heart beats, and the bottom number (diastolic) is the pressure between beats ^[2]. Low blood pressure, also called hypotension, is usually taken to mean a reading below 90/60 mmHg ^{[1, 3]}. NHLBI notes that normal adult blood pressure is usually under 120/80 mmHg ^[3].

For some people a low reading is normal for them and causes no trouble. MedlinePlus says low blood pressure is a problem mainly when it causes dizziness or fainting ^[2]. Others have low blood pressure because of a medical condition or a medicine ^[2]. The NHS adds that low blood pressure does not always cause symptoms, and that treatment may be needed if it does ^[1].

2. Causes and risk factors

Blood pressure rises and falls during the day with activity and emotions ^[1]. The NHS says some people are naturally low, sometimes because they are fit and healthy or because it runs in the family. Pressure can also fall with age and in pregnancy ^[1].

NHLBI lists several causes that need attention ^[3]:

• Problems with the autonomic nervous system, the part of the nervous system that controls blood pressure without you thinking about it, as seen in Parkinson's disease
• Blood loss
• Dehydration, which means the body has too little water
• Diabetes
• Heart problems, such as an irregular heartbeat
• Some medicines, especially those used to treat high blood pressure

Postural (orthostatic) hypotension is a drop in pressure when you stand up. The NHS describes it as dizziness or other symptoms after a sudden change of position ^[1]. MedlinePlus says some people feel symptoms when they stand up too quickly ^[2].

3. Signs and symptoms

Many people have no symptoms at all ^[3]. When symptoms occur, the NHS lists ^[1]:

• Feeling light-headed or dizzy
• Feeling sick
• Blurred vision
• General weakness
• Confusion
• Fainting

NHLBI adds tiredness, headache, neck or back pain and palpitations, which means being aware of your heartbeat ^[3].

4. Diagnosis and tests

The basic test is a blood pressure reading. The NHS says it can be taken by a pharmacist, a practice nurse or a doctor, or at home with a home monitor ^[1]. NHLBI says a doctor may also order blood, urine or imaging tests, and may use a tilt table test if fainting is frequent ^[3]. The NHS Check your blood pressure tool can help you understand a recent reading ^[1].

5. Treatment and self-care

Many people need no treatment ^[3]. NHLBI lists other options: drinking more fluids, changing or adjusting medicines, lifestyle changes and compression stockings for people who stand a lot ^[3]. If a cause is found, the doctor treats that cause. The NHS says that if a medicine is responsible, the doctor may change or adjust it, and that support stockings may be used ^[1]. Medicine to raise blood pressure is rarely needed, because lifestyle measures and treating the underlying cause usually help ^[1]. Never stop a prescribed medicine on your own.

Self-care steps suggested by the NHS and NHLBI include ^{[1, 3]}:

• Getting up slowly from sitting or lying down, and sitting down if you feel faint
• Drinking more fluids, unless your doctor has told you to limit them
• Eating small, regular meals and resting for a while after eating
• Avoiding standing still for long periods, sudden bending and too much alcohol

6. Special groups

NHLBI says older adults are at higher risk of low blood pressure, especially from medicines used to treat high blood pressure ^[3]. Pregnancy can lower blood pressure too ^{[1, 3]}. In both groups, a doctor can review medicines and advise on safe steps.

Checking your own blood pressure at home can help your doctor see a pattern. The NHS says readings can be taken with a home monitor, and the NHS Health Check offers adults aged 40 to 74 a blood pressure check at least every five years ^[1]. Keep a short note of when symptoms happen, what you were doing and which medicines you take, and bring it to your appointment. This helps the doctor find the cause and decide whether any change is needed.

7. When to see a doctor

The NHS advises seeing a doctor if dizziness or fainting keeps coming back ^[1]. NHLBI notes that many people have no symptoms and many need no treatment ^[3].

Signs of shock need immediate care. NHLBI lists cold, sweaty skin, fast breathing, bluish skin and a weak, rapid pulse ^[3].

In an emergency, call your local emergency number (112 in India, 911 in the United States).

8. Conclusion

A reading below 90/60 mmHg is not always a problem. If you feel well, it may simply be your normal level. If you have repeated dizziness, blurred vision or fainting, get your blood pressure checked and talk to your doctor, who can look for a cause and decide on any treatment.