Prone to passing out? Fainting often occurs when the blood pressure falls suddenly as you stand up.
Fainting can be scary. The good news is it’s usually nothing serious. GP Dr Roger Henderson explains the common causes of fainting, and what to do if you or someone else feels faint:
What is fainting?
Fainting is a brief episode of unconsciousness caused by a sudden drop in blood pressure, where not enough oxygen reaches your brain.
When someone faints they usually regain consciousness straight away, often after a brief period of confusion, and the cause of the faint is usually not serious. The person who has fainted may feel unwell for a brief time, with a full recovery taking several minutes. In general, the more someone faints, the more likely they are to faint again.
Why do people faint?
There are a great many possible causes for fainting. Common reasons include the following:
- Changes to the body’s blood pressure – usually due to low blood pressure – heart rate, or heart rhythm.
- Anaemia – where there are not enough red blood cells to carry adequate oxygen to your tissues.
- Poor circulation.
- Exhaustion or emotional stress.
- Pain Overheating and heat exhaustion.
- Some prescribed medications.
Fainting and blood pressure
Fainting often occurs when the blood pressure falls suddenly as you stand up – this is called orthostatic hypotension and is more common in older people. Dehydration, untreated or poorly controlled diabetes, some medicines (such as diuretics, which increase the production and flow of urine from the body, beta-blockers and some types of antidepressants) and health conditions that affect the nervous system, such as Parkinson’s disease, can all be triggers for orthostatic hypotension in some people.
Fainting often occurs when the blood pressure falls suddenly as you stand up.
A temporary drop in blood pressure can also be caused by prolonged standing (especially in hot weather), emotional distress, and the sight of blood or a hypodermic needle.
Less common reasons for fainting
The most common cause of blacking out is usually due to low blood pressure. But there are other causes including epileptic seizures and anxiety. Other possible reasons why there may be loss of consciousness include low blood sugar (hypoglycaemia), lack of oxygen from a variety of causes (hypoxia) and over-breathing (hyperventilation).
It is also possible to lose consciousness after a fall, a blow to the head or due to excess alcohol or other drugs. Strokes and mini strokes (transient ischaemic attacks) can also result in a loss of consciousness but a key point is that symptoms such as prolonged unconsciousness, confusion after the event, incomplete recovery and tongue biting all suggest that the cause is not a simple faint.
How can you tell you’re going to faint?
Fainting often happens very suddenly and the first thing someone usually knows about it is when they come round from the faint. But a faint may be preceded by other symptoms occurring just before one happens.
Premonitory symptoms include light headedness and dizziness, sweaty palms, nausea and fading vision.
These are called premonitory symptoms and include light headedness and dizziness, sweaty palms, nausea, fading vision and a general feeling of being unwell.
Sometimes, people who are about to faint and who recognise these signs lie down or elevate their legs to prevent a faint occurring. There may be a period of unconsciousness lasting for a few seconds but this is usually followed by a full recovery after a few minutes.
What to do if you feel faint
If you know or suspect that you are going to faint, try the following:
✔️ You should lie down, preferably in a position where your head is low and your legs are raised. This will encourage blood flow to the brain.
✔️ If it is not possible to lie down, sit down with your head between your knees.
✔️ Fresh air can also help, especially if you are feeling hot.
✔️ If you do faint, remain lying down for ten minutes.
✔️ Sit up slowly when you need to get up.
What to do if someone else faints
Help the person lie down but if they are unconscious, roll them onto their side. Check they are breathing and that they have a pulse. If possible, elevate the person’s feet above the height of their head.
Help the person lie down but if they are unconscious, roll them onto their side.
If the fainting episode was brought on by heat, remove or loosen clothes, and try to cool the person down by wiping them with a wet cloth or fanning them. In an emergency, call for medical assistance if the person has not regained consciousness within a few seconds or recovered in a few minutes.