Medical Matters > Symptom: Fainting

ME Essential Autumn 2017


Like most people with ME I have problems with balance and find it difficult to sustain any sort of activity that involves prolonged standing. I sometimes feel faint when standing up but have never actually fainted until recently. This has now happened on three occasions – all for no apparent reason. Fortunately, someone has always been with me and I haven’t injured myself. I usually recover very quickly but don’t normally feel as though I’m ‘back to normal’ till the next day. My GP took my pulse and blood pressure (which was low) and decided it was probably ‘just anther part of having ME’. I have been given some self-help advice about keeping well hydrated with water and not standing up too quickly but I’m concerned that there may be something else going wrong in addition to my ME. What would you advise?


There are a number of reasons why people with ME/CFS may feel faint, or actually have a fainting episode. The commonest explanation relates to what is called autonomic nervous system (ANS) dysfunction – the ANS is a key part of the nervous system that controls blood pressure and heart rate. One effect of this disturbance in normal control mechanisms is to cause an excessive fall in blood pressure when you move from lying to standing. This also causes a drop in blood flow to the brain, and if there isn’t enough blood reaching the brain on standing up, you will then feel faint and may even faint.

This explanation can be diagnosed by taking pulse and blood pressure measurements lying and standing. It may need to be further investigated by arranging a hospital investigation called a tilt table test. If this is the cause of your fainting we have ME Association information leaflets covering both orthostatic intolerance (problems with maintaining upright posture) and a condition called PoTS (postural orthostatic tachycardia syndrome) – where there is an exaggerated increase in pulse rate (= tachycardia) on standing. Other possible explanations include heart arrhythmias (which can be picked up on an ECG) and medical conditions like Addison’s disease (where levels of cortisol are very low and can present with ME/CFS like symptoms).

If the fainting episodes continue you must go back to your GP and ask if you could be referred to hospital for further assessment and investigation (which might include a tilt table test). Useful information from the NHS website on causes and management of fainting episodes:

See also: Dizziness and Dysautonomia.

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Medical Matters is for information purposes only. The answers provided by Dr Shepherd and the ME Association’s other expert advisers should not be construed as medical advice. We recommend that any information you deem relevant is discussed with your GP as soon as possible. It is important to obtain advice from a GP who is in charge of your clinical care, who knows you well, and who can consider other likely causes for symptoms. Seek personalised medical advice whenever a new symptom arises, or an existing symptom worsens. Don't assume that new or worsened symptoms are a result of having ME/CFS.

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