Low Blood Pressure Symptoms: What They Mean and What to Do

What counts as low blood pressure

Blood pressure has two numbers. The top (systolic) number is the pressure when the heart beats, and the bottom (diastolic) is the pressure between beats. Readings below 90/60 mmHg are generally called low. A healthy adult's normal range is roughly 90/60 to 120/80.

What matters most is how you feel and whether your blood pressure has dropped from your usual level. A fall from 150 to 100 can cause symptoms even though 100 is "normal". For the medical background on types and treatment, see hypotension.

Symptoms of low blood pressure

When blood pressure falls too low, less blood reaches the brain and other organs, causing:

• dizziness or light-headedness, especially on standing up
• blurred or dimming vision
• feeling weak, tired or "washed out"
• nausea
• feeling faint or fainting
• difficulty concentrating
• pale, cold or clammy skin
• fast or shallow breathing
• a racing heartbeat as the heart tries to compensate

Symptoms are often worse in the morning, after hot showers, after large meals, after standing still, and in hot weather.

Common causes

Standing up (orthostatic or postural hypotension)

When you stand, about half a liter of blood pools in the legs. Normally, reflexes tighten blood vessels and speed the heart within seconds. If these reflexes are slow, blood pressure drops and you feel dizzy. Orthostatic hypotension is common in older adults, with dehydration, and with certain medicines.

Dehydration

Not drinking enough, sweating in heat, fever, vomiting and diarrhea all reduce blood volume. See dehydration.

Medicines

• blood pressure medicines, especially when started, increased or combined
• diuretics (water pills)
• alpha-blockers for prostate symptoms (tamsulosin, doxazosin)
• nitrates for angina, and erectile dysfunction medicines (never take these together)
• antidepressants, antipsychotics and Parkinson's medicines
• opioids and sedatives

Other everyday causes

• After meals (postprandial hypotension): blood diverts to the gut, common in older adults
• Alcohol
• Reflex fainting (vasovagal): triggered by pain, the sight of blood or prolonged standing
• Pregnancy: blood pressure normally falls in the first 24 weeks
• Prolonged bed rest

Serious causes

• Blood loss: from injury, internal bleeding, heavy periods or a bleeding ulcer
• Sepsis: severe infection widens blood vessels throughout the body
• Anaphylaxis: severe allergic reaction
• Heart problems: very slow heart rate, heart attack, heart failure, valve disease
• Hormone problems: Addison's disease (adrenal insufficiency), underactive thyroid, low blood sugar
• Nerve damage affecting blood pressure control, from diabetes, Parkinson's disease or multiple system atrophy

What to do when your blood pressure is low

If you feel dizzy or faint:

1. Sit or lie down immediately. Raise your legs if you can.
2. Drink a glass or two of water.
3. Stand up slowly once you feel better: sit on the edge of the bed for a minute, then stand.
4. Do not drive until you feel completely normal.

To prevent symptoms:

• Drink enough fluid, around 6 to 8 glasses a day, more in heat or illness.
• Get up slowly, especially in the morning. Flex your calves and pump your feet before standing.
• Eat smaller meals and limit alcohol and refined carbohydrates if you get dizzy after eating.
• Avoid long, hot showers and standing still for long periods.
• Wear compression stockings if advised.
• Ask your doctor whether a little extra salt is safe for you. It is not suitable for people with heart failure or kidney disease.
• Ask your doctor to review your medicines. Do not stop a prescribed medicine on your own.

When to see a doctor

See a doctor if you have frequent dizziness, fainting, or low readings with symptoms. They will check your blood pressure lying and standing, review your medicines, and may order blood tests (blood count, kidney function, blood sugar, cortisol), an ECG, or an echocardiogram.

Frequently asked questions

What are the symptoms of low blood pressure?

The main symptoms are dizziness or light-headedness, especially on standing, blurred vision, tiredness, weakness, nausea, difficulty concentrating and fainting. Severe low blood pressure can cause confusion, cold clammy skin and fast breathing, which are signs of shock.

Is 90/60 low blood pressure?

Yes, 90/60 mmHg is the usual cutoff for low blood pressure. Many healthy people have readings around this level without any symptoms, and it is not a problem for them. It only needs attention if it causes dizziness, fainting or other symptoms.

What should I do if my blood pressure is low?

Sit or lie down, raise your legs and drink water. Stand up slowly when you feel better. If you have confusion, chest pain, cold clammy skin or fainting, call 911 or your local emergency number. Frequent symptoms should be checked by a doctor.

What is a dangerously low blood pressure?

A systolic reading below 90 mmHg with symptoms such as confusion, cold or clammy skin, a weak rapid pulse or fast breathing can be dangerous, because organs are not getting enough blood. It needs emergency care. The number alone matters less than these signs.

Can dehydration cause low blood pressure?

Yes. Dehydration reduces the amount of blood in circulation, which lowers blood pressure, especially on standing. Heat, exercise, fever, vomiting and diarrhea are common causes. Drinking fluids usually brings it back up quickly.