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Low blood pressure

198 Geriatric Medicine doctors in Hong Kong →

Also known as: Low blood pressure (spoken order) · Postural hypotension · Orthostatic hypotension ·

A low reading is not in itself a disease, and Hong Kong has no threshold below which low blood pressure is diagnosed. One form of it is defined, however: the Hospital Authority states that a fall of 20 mmHg systolic or 10 mmHg diastolic on standing is postural hypotension, with blurred vision, dizziness and weakness among its signs, fainting in severe cases, and an increased risk of falling.

Hong Kong has 198 registered Geriatric Medicine doctors.

Source: Medical Council of Hong Kong register · read 2026-09-21

ok.med editorial team ·
Compiled by the editorial team from the sources listed below. Not reviewed by an individual doctor.

How low is low?

Hong Kong publishes no official threshold below which low blood pressure is diagnosed. What the Centre for Health Protection does publish is the upper end: normal blood pressure keeps systolic below 120 mmHg and diastolic below 80 mmHg, while 140 or 90 and above, sustained, is hypertension.

The asymmetry has a reason. High blood pressure damages vessels while causing no sensation at all, so it needs a numeric line. A low reading generally becomes clinically meaningful only once there are signs — dizziness, blurred vision, weakness. What matters is whether there are symptoms, not the reading alone.

A healthy person with no complaints who records a lowish reading does not necessarily have a problem. The form that is defined, and for which Hong Kong publishes clinical guidance, is postural hypotension — the next section.

Blood pressure reference values (Centre for Health Protection) and the postural hypotension threshold (Hospital Authority)
CategoryValue
NormalSystolic below 120 and diastolic below 80 mmHg
Pre-hypertensionSystolic 120–139, or diastolic 80–89 mmHg
HypertensionSystolic sustained at 140 or above, or diastolic at 90 or above
Low blood pressureNo published diagnostic figure in Hong Kong; generally judged on whether there are symptoms
Postural hypotensionA fall of 20 mmHg systolic, or 10 mmHg diastolic, on standing from lying

What is postural hypotension?

The Hospital Authority describes it as low blood pressure arising from a change of posture — suddenly standing from lying, or standing for a long period — producing insufficient blood supply to the brain. It is generally taken to mean a fall of 20 mmHg systolic or 10 mmHg diastolic on standing from lying.

The signs it lists are blurred vision, dizziness, weakness, and fainting in severe cases; and it states plainly that these raise the risk of falling. That sentence is the most important on this page: in an older person the consequence is usually not the blood pressure itself but the fall.

What causes low blood pressure?

The Hospital Authority groups the causes of postural hypotension into four: insufficient circulating volume, autonomic nervous system dysfunction, medication, and cardiac problems.

Insufficient circulating volume covers conditions causing substantial fluid loss — fever, vomiting, diarrhoea — as well as blood loss and anaemia. On the autonomic side, a healthy person standing suddenly from lying activates mechanisms that hold blood pressure steady; in older people the decline of nervous system function unbalances that regulation. Neuropathy from diabetes, from long-term alcohol use, from spinal nerve injury or following viral infection can all impair autonomic function.

Among medicines the Hospital Authority lists antihypertensives, cardiac drugs and antidepressants. This needs stating plainly: knowing that a class of medicine can cause postural hypotension is not a reason to stop taking it. Stopping medication that controls blood pressure or heart disease can have serious consequences, and any adjustment is for the prescribing doctor to make.

On the cardiac side, besides myocardial infarction the Authority names arrhythmia, severe heart failure, cardiomyopathy and aortic stenosis as limiting cardiac output and so producing postural hypotension. It also states that treating postural hypotension begins with identifying the likely underlying cause and treating that.

Medical Council of Hong Kong register

198 Geriatric Medicine doctors in Hong Kong

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When do the symptoms appear?

The Hospital Authority lists the moments when circulatory demand rises suddenly: moving, sitting up or standing abruptly; on waking in the morning, when blood pressure is naturally lower; and after eating, because digestion draws blood — particularly after a large meal or sugary food.

The rest of the list: alcohol has a similar effect; straining when constipated or passing urine with difficulty; overheated surroundings; and anxiety causing overbreathing, which lowers blood pressure in turn. The list explains why episodes tend to recur in particular situations — on rising, after meals, in the bathroom, in hot weather — rather than at random.

What should be done during an episode?

The Hospital Authority’s steps: stop what you are doing; sit down, and lie down if possible; if fully conscious, take some water; once the symptoms settle, get up slowly; and if things do not improve, seek help from a healthcare professional as soon as possible.

The order is the point. Stopping and getting low comes first because the danger during dizziness is the fall; and getting up slowly is placed after the symptoms settle, because standing too quickly again is exactly what brings them back.

How can the risk of falling be reduced?

The Hospital Authority’s advice concentrates on the moment of changing position: perform counter-pressure manoeuvres and muscle contractions beforehand; after sitting up, wait about one minute and watch for severe dizziness; and the same movements can be done while seated, to help the body adapt to the change.

Other measures: use a suitable walking aid, one fitted with a seat and brakes, to lower the risk of a fall; and if faintness or its warning signs appear while changing position or walking, perform counter-pressure manoeuvres at once to increase venous return and reduce the chance of falling. In bed, raise the pillow so the head sits slightly higher than the heart; before rising, move the legs and sit on the edge of the bed for several minutes before standing.

At a glance

Postural hypotension: a fall of 20 mmHg

Postural hypotension: a fall of 20 mmHg systolic or 10 mmHg diastolic on standing from lying. Signs include blurred vision, dizziness and weakness, fainting in severe cases, and an increased risk of falling. The Hospital Authority advises waiting about one minute after sitting up, moving the legs and sitting on the edge of the bed for several minutes before standing, eight cups — around two litres — of fluid a day, and smaller more frequent meals.
Data: Hospital Authority New Territories West Cluster (Geriatrics, Physiotherapy, Occupational Therapy) · Read the original ›

What daily and dietary measures help?

The Hospital Authority’s dietary advice: take enough fluid — eight cups a day, around two litres in total, including water, plain tea and clear soup; avoid large meals and eat smaller ones more often; avoid alcohol; and before exercise take 400 to 500 ml, about two cups, to raise blood pressure.

It also notes that seasoning need not be unduly restricted and may be used in moderation for flavour; that the diet should be balanced and nutritionally adequate; and that fibre — wholegrains, vegetables and fruit — should be eaten daily to prevent constipation, which ties back to an earlier point, since straining is one of the moments that brings symptoms on.

On daily living it emphasises keeping blood glucose to target and avoiding hypoglycaemia, screening for and treating chronic diabetic complications, and monitoring blood pressure; eating sensibly rather than to excess or hunger, and not standing or exerting oneself immediately after a meal; avoiding spirits; drinking more water to raise blood volume and so blood pressure; replacing salt and water after sweating heavily; and rising slowly.

Which specialty follows this up in Hong Kong?

The only Hong Kong material on managing postural hypotension is issued by the Hospital Authority’s New Territories West Cluster Department of Medicine and Geriatrics (Geriatrics), together with the cluster’s physiotherapy and occupational therapy departments.

That reflects how it is handled: managing postural hypotension is not only prescribing, but training in how to change position, selecting a walking aid, and adjusting the home — physiotherapy and occupational therapy territory. The Authority states that both drug and non-drug treatment can effectively reduce postural hypotension and its signs.

A first episode, or repeated episodes, should be assessed by a doctor to establish the cause. This page recommends no medicine and no dose and assesses no individual case; interpreting a reading requires history, medication and examination together, and those belong in a consultation.

What do the Hong Kong authorities say?

Postural hypotension is one of the few conditions for which the Hospital Authority issues management material directly, and that material is specific down to millimetres of mercury, minutes and millilitres. Each item below carries its source and the date it was read.

  • The Hospital Authority states that a fall of 20 mmHg systolic, or 10 mmHg diastolic, on standing from lying is generally taken to be postural hypotension; the accompanying signs include blurred vision, dizziness and weakness, with fainting in severe cases, and these signs increase the risk of falling.Hospital Authority New Territories West Cluster: managing postural hypotension · read · (source)
  • The Hospital Authority groups the causes into four: insufficient circulating volume (fever, vomiting, diarrhoea, blood loss, anaemia); autonomic dysfunction (age-related decline, diabetic neuropathy, long-term alcohol use, spinal nerve injury, post-viral neuropathy); medication (antihypertensives, cardiac drugs, antidepressants); and cardiac problems (myocardial infarction, arrhythmia, severe heart failure, cardiomyopathy, aortic stenosis).Hospital Authority New Territories West Cluster: managing postural hypotension · read · (source)
  • The Hospital Authority advises counter-pressure manoeuvres and muscle contractions before changing position; waiting about one minute after sitting up while watching for severe dizziness; and using a walking aid fitted with a seat and brakes to lower the risk of a fall.Hospital Authority New Territories West Cluster: managing postural hypotension · read · (source)
  • The Hospital Authority advises eight cups of fluid a day, about two litres in total, including water, plain tea and clear soup; avoiding large meals in favour of smaller more frequent ones; avoiding alcohol; and taking 400 to 500 ml, about two cups, before exercise to raise blood pressure.Hospital Authority New Territories West Cluster: managing postural hypotension · read · (source)
  • The Centre for Health Protection’s reference values are that an adult’s normal blood pressure keeps systolic below 120 mmHg and diastolic below 80 mmHg, and that sustained systolic of 140 or above, or diastolic of 90 or above, is hypertension. The Centre publishes no diagnostic figure for low blood pressure.Centre for Health Protection: hypertension · read · (source)

When should help be sought promptly?

  • Having fainted, or nearly fallen, with dizziness or blacking out — the Hospital Authority notes these signs raise the risk of a fall.
  • Dizziness on standing becoming more frequent, or taking longer to pass.
  • Chest pain, an irregular heartbeat or breathlessness alongside it — the Authority lists arrhythmia, heart failure and aortic stenosis among possible causes.
  • Marked dehydration from fever, vomiting or diarrhoea, or any blood loss.
  • A suspicion that a current medicine is involved. Raise it with the prescribing doctor; do not stop it or change the dose yourself.

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Conditions related to Low blood pressure

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Frequently asked questions

Below what reading is blood pressure considered low?
Hong Kong publishes no diagnostic figure for low blood pressure. What the Centre for Health Protection publishes is the upper end — normal is systolic below 120 and diastolic below 80 mmHg. What is defined is postural hypotension: a fall of 20 mmHg systolic or 10 mmHg diastolic on standing.
A low reading but no symptoms — does it need dealing with?
A lowish reading is not in itself a sign of disease. Low blood pressure generally becomes clinically meaningful once there are signs — dizziness, blurred vision, weakness. If in doubt, a doctor should assess it alongside history and medication rather than the reading alone.
On blood pressure medicine and the reading is low — should it be stopped?
Not on your own. The Hospital Authority does list antihypertensives, cardiac drugs and antidepressants among the causes of postural hypotension, but stopping medicine that controls blood pressure or heart disease can have serious consequences. Raise it with the prescribing doctor and let them decide.
Why does standing up so often bring on dizziness?
The Hospital Authority explains that standing suddenly from lying normally triggers mechanisms that hold blood pressure steady, and that in older people age-related decline of the nervous system unbalances this. It also notes blood pressure is naturally lower on waking, making getting up one of the commonest moments for symptoms.
Is dizziness after meals related?
Yes. The Hospital Authority lists after eating among the moments symptoms may appear, because digestion draws blood — particularly after a large meal or sugary food — and alcohol has a similar effect. Its advice is to avoid large meals in favour of smaller ones, and not to stand or exert yourself straight after eating.
How long should one wait before standing?
The Hospital Authority advises waiting about one minute after sitting up while watching for severe dizziness, and before getting out of bed moving the legs first and sitting on the edge for several minutes before standing.

Sources

  1. Hospital Authority New Territories West Cluster, Department of Medicine and Geriatrics (Geriatrics) with the physiotherapy and occupational therapy departments: managing postural hypotension — the definition, signs, four groups of causes, when symptoms appear, what to do in an episode, fall prevention, and daily and dietary advice. Hospital Authority, New Territories West Cluster ()
  2. Centre for Health Protection: hypertension — the reference values, showing that Hong Kong publishes the upper end and no diagnostic figure for low blood pressure. Centre for Health Protection, Department of Health ()
  3. Centre for Health Protection: hypertension, the silent killer — the definition of hypertension and the pre-hypertension boundary. Centre for Health Protection, Department of Health ()
  4. Department of Health Elderly Health Service: hypertension — blood pressure management in older people, used here for contrast with what low blood pressure means in the same group. Elderly Health Service, Department of Health ()

This page is compiled from the Hong Kong official sources listed above. It is general information only — not a diagnosis, a treatment recommendation or medical advice, and no substitute for seeing a doctor. If you are unsure or your condition changes, consult a registered doctor.