Low blood pressure (hypotension)
A reading below 90/60 mmHg is conventionally called low blood pressure. Unlike high pressure, though, low pressure is not in itself a disease: a great many…
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Medicines commonly prescribed for Low blood pressure (hypotension)
For informational purposes only. Always consult a doctor before using any medicine.
Dosage form: TABLET, Fludrocortisone 0.1 mgActive substance: fludrocortisoneManufacturer: Laboratorios Ern S.A.Prescription requiredDosage form: TABLET, 5 mgActive substance: midodrineManufacturer: Cheplapharm Arzneimittel GmbhPrescription required
A reading below 90/60 mmHg is conventionally called low blood pressure. Unlike high pressure, though, low pressure is not in itself a disease: a great many perfectly healthy people run low all their lives and nothing whatever follows from it. What matters is not the numbers on the monitor but two other questions. First, is it making you feel unwell. Second, is something behind the drop that needs finding.
When low pressure is simply normal
The 90/60 line is a convention; there is no single threshold, and a monitor on its own makes no diagnosis. In fit people, in slim people, in young women, the pressure often sits low for decades — a sign of blood vessels working well rather than of anything broken. It also shifts through the day: lower at night and in the early morning, lower in hot weather, after a heavy meal, after a hot bath and after alcohol.
If you feel well, there is nothing to raise: "getting the pressure up to normal" is a pointless goal in itself. Three situations do deserve attention: the pressure is causing symptoms; it has fallen noticeably compared with what is usual for that person; the drop has appeared alongside other signs of illness. The second point matters more than it looks. For someone who has lived with high blood pressure for years, 110/70 may already be low and produce the whole picture of light-headedness.
What it feels like
- Dizziness and light-headedness, especially in the first seconds after standing up.
- Vision going dark, spots dancing, the field of view narrowing for a moment.
- Weakness, tiring quickly, drowsiness, a fog in the head.
- Nausea, pallor, clammy sweat, sometimes yawning just before a wave of faintness.
- Fainting.
In older people all of this looks different and is therefore missed. What comes to the fore are falls with no clear explanation, unsteadiness, confusion and general weakness, while dizziness may never be mentioned at all. If an older person has started falling, taking the blood pressure standing up is one of the first sensible things to do.
The pressure that drops on standing
The moment you stand, around half a litre of blood moves downwards into the vessels of the legs and abdomen. Normally the vessels tighten in response, the pulse quickens slightly, and the pressure holds within seconds. When that reflex is slow, the brain is briefly left short of blood — hence both the darkening vision and the faint.
Checking for it is simple: the pressure is measured lying down after five minutes of rest, then standing, at one minute and at three. A fall of 20 or more in the upper figure, or 10 or more in the lower, means postural hypotension. With these complaints that measurement tells you more than anything else, and it is the one most often left undone.
Two related states are worth telling apart. A fall in pressure after eating: blood is redirected to the stomach and bowel, and half an hour to an hour later weakness rolls in. It occurs mainly in older people and in long-standing diabetes, and what helps is not a drug but smaller portions. A vasovagal faint is the commonest cause of fainting altogether: at the sight of blood, from pain or fear, in a stuffy room, after long standing, with coughing, straining or passing urine. It is harmless in itself, but learning to recognise the warning signs and lie down in time does matter — injuries from the fall are more dangerous than the faint.
Why the pressure falls
There are many causes, and the commonest is checked first.
- Medicines. Blood pressure drugs, diuretics, nitrates, alpha blockers (including those prescribed to men for an enlarged prostate), some antidepressants, drugs for Parkinson's disease. Two or three of these together add up to more than the sum of their parts.
- Not enough fluid: hot weather, vomiting, diarrhoea, drinking too little, diuretics.
- Blood loss, including the unnoticed kind: bleeding from the stomach or bowel, heavy periods.
- Pregnancy. The pressure falls naturally in the second trimester, and that is normal.
- Disturbed automatic control: long-standing diabetes, Parkinson's disease, certain kinds of nerve damage.
- Heart conditions: a weak heart muscle, too slow a pulse, rhythm disorders, narrowing of the aortic valve.
- Hormonal causes: an underactive thyroid gland and — rare but the most important item on this list — adrenal insufficiency.
- Anaemia and vitamin B12 deficiency.
- Circumstances: long bed rest, standing still for a long time, alcohol, heat, a hot bath.
Adrenal insufficiency deserves a paragraph of its own: it is easy to miss and expensive to get wrong. What raises suspicion is a combination — persistent weakness, unexplained weight loss, nausea, a craving for salty food, darkening of the skin (particularly the creases of the palms, scars and gums) and low pressure with no other explanation; blood tests usually show a low sodium. Its danger is the crisis: an abrupt collapse of pressure with vomiting, abdominal pain and confusion, set off by an infection, an injury or an operation. A crisis needs help immediately, while the condition itself responds well to hormone replacement taken permanently.
When help cannot wait
Low pressure becomes dangerous when organs stop receiving enough blood. Call an ambulance (in European countries the single number 112) if:
- the person is unconscious and cannot be roused, or is not breathing;
- the pressure has dropped and the skin is cold, clammy, pale or mottled, the pulse is fast and weak, the mind is confused and there is almost no urine — this is shock;
- there are signs of bleeding: vomiting blood or what looks like coffee grounds, black tarry stools, heavy bleeding from the womb;
- the drop comes with fever and shivering — this may be blood poisoning;
- a rash, swelling of the lips and tongue and noisy laboured breathing follow an insect sting, a medicine or a food — this is anaphylaxis;
- the drop is accompanied by chest pain, severe breathlessness, a sudden severe headache or back pain;
- the faint happened during exertion, while lying down, or alongside violent palpitations — that is how dangerous rhythm disorders announce themselves.
Without an ambulance but on the same day, see a doctor if faints keep recurring, if the pressure dropped soon after a new medicine was started, if the drop comes with weight loss or darkening skin, or if the head was struck during a fall.
How to measure it, and what a doctor will check
Only a properly taken reading is worth anything. The cuff must fit the upper arm; sit with your back supported and your legs uncrossed, arm at the level of the heart; rest quietly for five minutes beforehand and avoid smoking and coffee for half an hour. Take two or three readings a minute apart and write them all down. At home it helps to keep a diary for several days — morning, evening, and above all the moments when the faintness comes. Wrist devices are less accurate than upper-arm ones. And measure separately lying and standing: that pair of figures explains the complaints more often than anything else.
At the appointment the doctor will go through the list of medicines first. After that the usual tests are a full blood count, glucose, sodium and potassium, kidney and thyroid function, and a tracing of the heart. Where hidden blood loss is suspected, the stool is tested for blood and the ferritin measured; where adrenal insufficiency is suspected, a morning cortisol. Sometimes continuous pressure or rhythm monitoring is needed, or a test involving a long period upright on a tilting table.
What you can do yourself
- Stand up in two stages. Sit first, wait half a minute, wiggle your feet, clench and unclench your fists, and only then rise; getting out of bed in the morning especially unhurriedly.
- Do not try to ride out the faintness standing. At the first warning, sit or lie down and raise your legs. If there is nowhere to lie, cross your legs and squeeze the thigh and buttock muscles hard, clench your fists: this lifts the pressure within seconds.
- Drink enough, particularly in heat and during physical work. A glass or two of cool water drunk quickly raises the pressure noticeably for about half an hour — worth using before leaving the house.
- Salt. There is no reason to restrict it without cause, and where fainting is a problem a doctor may advise eating more salt than usual. Only by agreement, though: with heart or kidney failure that advice is dangerous.
- Eat more often and in smaller amounts, fewer fast carbohydrates at a sitting, and do not jump up after a heavy meal.
- Compression hosiery for the calves and thighs, sometimes an elastic abdominal binder: it stops blood pooling low down.
- Raise the head of the bed by ten to fifteen centimetres — this reduces overnight fluid loss and the morning drop.
- Avoid standing still for long periods, hot baths and saunas, overheating, alcohol.
- Keep moving. Swimming, cycling and exercises done semi-reclined are tolerated best, while giving up activity only makes upright posture harder to bear.
When treatment is prescribed
The cause is treated, not the number. The most effective single step is usually work on the medicine list: stopping what is unnecessary, substituting, lowering a dose, or simply moving a tablet to a different time of day. After that, as the case requires — replacing fluid, treating anaemia, the thyroid, adrenal insufficiency.
Drugs to raise the pressure itself are rarely needed. They are used when lifestyle measures have been exhausted and life is still restricted: agents that tighten the blood vessels, and agents that make the body hold on to sodium and water. Both classes call for care, because they can push the pressure up while you are lying down, so that is watched separately. If the cause is too slow a pulse, a pacemaker settles the question. And for ordinary vasovagal faints, medicines are usually not needed at all: recognising the warning signs, the muscle-tensing manoeuvres and drinking enough are what work.
Online consultation
This subject is almost entirely suited to a remote appointment, because what counts here is conversation and figures rather than examination. The doctor will ask exactly when the faintness comes, and from that alone will separate a drop on standing from a drop after eating and from an ordinary vasovagal faint. They will look through your diary of readings, explain how to take the pressure lying and standing properly, and go through the test results. The most valuable part of such an appointment is the review of medicines: very often the cause sits right there and can be removed with no treatment at all. Online you can settle how much to drink and what to do about salt given your other conditions, choose compression hosiery, sort out blood pressure in pregnancy, and decide which investigations are genuinely needed. And the doctor will spell out separately the signs that call not for a message but for an ambulance.
This material is for information only and does not replace medical advice.
Consult with a doctor about Low blood pressure (hypotension)
Discuss your symptoms and possible next steps with a doctor online.
Online doctors for Low blood pressure (hypotension)
Discuss your symptoms and possible next steps for Low blood pressure (hypotension) with a doctor online.
