What can cause you to have low blood pressure

Symptoms of low blood pressure

Get your blood pressure checked if you keep getting symptoms like:

• lightheadedness or dizziness
• feeling sick
• blurred vision
• generally feeling weak
• confusion
• fainting

This might mean your blood pressure is too low.

If you get symptoms when you stand up or suddenly change position, you may have postural hypotension.

How to check your blood pressure

You can check your blood pressure:

• by asking if a pharmacist can do it
• by asking a practice nurse or GP to do it
• at home yourself using a home blood pressure monitor – Blood Pressure UK has information about choosing a blood pressure monitor

Low blood pressure is a measurement of less than 90/60mmHg.

Important: Regular blood pressure check

If you're 40 to 74 years old, you should have your blood pressure checked at least once every 5 years as part of the NHS Health Check.

Non-urgent advice: See a GP if:

• you keep getting symptoms such as dizziness and fainting

Treatment for low blood pressure depends on the cause

If a cause can be found, a GP will be able to recommend treatment to ease your symptoms.

For example, they may suggest:

• changing medicines or altering your dose, if this is the cause
• wearing support stockings – this can improve circulation and increase blood pressure

Medicine to increase blood pressure is rarely needed because simple lifestyle measures or treating the underlying cause is usually effective.

How to ease low blood pressure symptoms yourself

Do

• get up slowly from sitting to standing

• take care when getting out of bed – move slowly from lying to sitting to standing

• eat small, frequent meals – lying down or sitting still for a while after eating may also help

• increase the amount of water you drink

Don’t

• do not sit or stand for long periods

• do not bend down or change posture suddenly

• do not drink caffeinated drinks at night

• do not drink too much alcohol

Causes of low blood pressure

Your blood pressure can vary depending on the time of day. It gradually increases throughout the day.

What you're doing and how you're feeling can also affect it.

There are many possible causes of low blood pressure. It may be low because you're fit and healthy, or you may have inherited it from your parents.

Within certain limits, the lower your blood pressure reading is, the better. There is also no specific number at which day-to-day blood pressure is considered too low, as long as none of the symptoms of trouble are present.

Symptoms of low blood pressure

Most doctors will only consider chronically low blood pressure as dangerous if it causes noticeable signs and symptoms, such as:

• Dizziness or lightheadedness
• Nausea
• Fainting (syncope)
• Dehydration and unusual thirst
• Dehydration can sometimes cause blood pressure to drop. However, dehydration does not always cause low blood pressure. Fever, vomiting, severe diarrhea, overuse of diuretics and strenuous exercise can all lead to dehydration, a potentially serious condition in which your body loses more water than you take in. Even mild dehydration (a loss of as little as 1 percent to 2 percent of body weight) can cause weakness, dizziness and fatigue.
• Lack of concentration
• Blurred vision
• Cold, clammy, pale skin
• Rapid, shallow breathing
• Fatigue
• Depression

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Underlying causes of low blood pressure

Low blood pressure can occur with:

• Prolonged bed rest
• Pregnancy: During the first 24 weeks of pregnancy, it’s common for blood pressure to drop.
• Decreases in blood volume: A decrease in blood volume can also cause blood pressure to drop. A significant loss of blood from major trauma, dehydration or severe internal bleeding reduces blood volume, leading to a severe drop in blood pressure.
• Certain medications: A number of drugs can cause low blood pressure, including diuretics and other drugs that treat hypertension; heart medications such as beta blockers; drugs for Parkinson’s disease; tricyclic antidepressants; erectile dysfunction drugs, particularly in combination with nitroglycerine; narcotics and alcohol. Other prescription and over-the-counter drugs may cause low blood pressure when taken in combination with high blood pressure medications.
• Heart problems: Among the heart conditions that can lead to low blood pressure are an abnormally low heart rate (bradycardia), problems with heart valves, heart attack and heart failure. Your heart may not be able to circulate enough blood to meet your body’s needs.
• Endocrine problems: Such problems include complications with hormone-producing glands in the body’s endocrine systems; specifically, an underactive thyroid (hypothyroidism), parathyroid disease, adrenal insufficiency (Addison’s disease), low blood sugar and, in some cases, diabetes.
• Severe infection (septic shock): Septic shock can occur when bacteria leave the original site of an infection (most often in the lungs, abdomen or urinary tract) and enter the bloodstream. The bacteria then produce toxins that affect blood vessels, leading to a profound and life-threatening decline in blood pressure.
• Allergic reaction (anaphylaxis): Anaphylactic shock is a sometimes-fatal allergic reaction that can occur in people who are highly sensitive to drugs such as penicillin, to certain foods such as peanuts or to bee or wasp stings. This type of shock is characterized by breathing problems, hives, itching, a swollen throat and a sudden, dramatic fall in blood pressure.
• Neurally mediated hypotension: Unlike orthostatic hypotension, this disorder causes blood pressure to drop after standing for long periods, leading to symptoms such as dizziness, nausea and fainting. This condition primarily affects young people and occurs because of a miscommunication between the heart and the brain.
• Nutritional deficiencies: A lack of the essential vitamins B-12 and folic acid can cause anemia, which in turn can lead to low blood pressure.

If you notice a sudden decline in blood pressure

A single lower-than-normal reading is not cause for alarm, unless you are experiencing any other symptoms or problems. If you experience any dizziness, lightheadedness, nausea or other symptoms, it’s a good idea to consult with your health care professional. To help with your diagnosis, keep a record of your symptoms and activities at the time they occurred.

Is low blood pressure related to low heart rate? Find out.

Written by American Heart Association editorial staff and reviewed by science and medicine advisers. See our editorial policies and staff.

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