What Is Low Blood Pressure? Causes, Symptoms and When to See a Doctor

High blood pressure gets most of the attention, so people are often unsettled when a reading comes back unusually low. The reassuring answer, most of the time, is that a low number by itself is not a disease. What matters is whether it is causing symptoms — and whether something treatable is driving it.

What counts as low

A reading below roughly 90/60 mmHg is conventionally called hypotension. But the threshold is far less meaningful than for high blood pressure, because normal varies so much between people. Young, slim, physically fit adults often run in the 90s and feel perfectly well; that is their baseline, not an illness.

The clinically useful question is not "is the number low" but "is the brain and are the organs getting enough blood". A person whose pressure has always been 95/60 and feels fine needs nothing. A person whose usual 140/85 has fallen to 100/60 may be seriously unwell, despite a number that still looks acceptable.

Symptoms that suggest it matters

• Dizziness or lightheadedness, especially on standing up
• Blurred or greying vision for a few seconds after rising
• Unusual fatigue and poor concentration
• Nausea
• Feeling faint, or actually fainting
• Cold, clammy or pale skin

The commonest pattern: dizziness on standing

Orthostatic hypotension is a fall in pressure within about three minutes of standing. Blood pools in the legs and, for a moment, the circulation does not compensate quickly enough. It becomes more common with age, and it is a genuine cause of falls and fractures in older adults — which is why it is worth investigating rather than dismissing.

A related pattern is a drop after meals, particularly large carbohydrate-heavy ones, as blood is diverted to the gut.

Causes worth knowing about

• Dehydration. In Chennai's heat this is easily the most frequent and most overlooked cause — through sweating, inadequate fluid intake, fever, vomiting or diarrhoea.
• Medications. Blood pressure tablets, diuretics, alpha blockers used for prostate symptoms, nitrates, some antidepressants and Parkinson's drugs. Dose changes and drug interactions are a common trigger.
• Blood loss, including slow, hidden loss from the gut, which may show as black stools or unexplained anaemia.
• Heart problems — a very slow or very fast rhythm, valve disease, weakened heart muscle, or a heart attack.
• Hormonal conditions such as adrenal insufficiency or thyroid disease, and autonomic nerve damage from long-standing diabetes.
• Pregnancy, where pressure normally dips in the first two trimesters.
• Severe infection or allergic reaction, which can cause a dangerous collapse in pressure.

When low blood pressure is an emergency

Seek immediate care for low pressure with any of the following:

• Chest pain or breathlessness
• Confusion, drowsiness or difficulty rousing someone
• Cold, clammy, mottled skin with a fast weak pulse
• Fainting, particularly without warning, during exertion, or with injury
• Black tarry stools, vomiting blood, or heavy bleeding
• Fever with a rapidly dropping pressure
• Swelling of lips or tongue, rash and breathing difficulty after a sting, food or medicine

Fainting during exercise, or fainting with no warning at all, deserves cardiac assessment rather than reassurance.

How it is assessed

A proper evaluation starts with blood pressure measured both lying and standing, a pulse check, and a careful review of every medication you take, including ones bought without prescription. From there, tests are directed by what the history suggests — blood counts and electrolytes, thyroid and glucose, an ECG, and where indicated an echocardiogram, a Holter monitor to catch intermittent rhythm problems, or a tilt table test for recurrent unexplained fainting.

What helps

Treatment follows the cause. Where no serious underlying condition is found, simple measures resolve most cases:

• Increase fluid intake, particularly in hot weather and before prolonged standing
• Rise in stages — sit on the edge of the bed for a few moments before standing
• Eat smaller, more frequent meals if symptoms follow eating
• Compression stockings, where advised, reduce pooling in the legs
• Avoid prolonged motionless standing and very hot baths
• Ask your doctor to review your prescriptions — adjusting a dose or timing often fixes the problem entirely

Adding salt is sometimes recommended, but only on medical advice — it is unsuitable for anyone with heart failure, kidney disease or a history of high blood pressure. Medication to raise pressure is reserved for a small number of people with persistent, disabling symptoms.

If you have repeated dizziness on standing, have fainted, or have noticed your usual readings falling without explanation, the cardiology team at Iswarya Hospital can establish whether it reflects a benign pattern or something that needs treating.

This article provides general health information and is not a substitute for personal medical advice. Please consult a qualified doctor about your own symptoms, medications and treatment.