Dr Charles Shepherd, Honorary Medical Adviser to the ME Association has updated the ME Association's information on Orthostatic Intolerance (OI).
This free comprehensive booklet covers everything you need to know about OI in relation to ME/CFS and Long Covid.
Introduction – What is Orthostatic Intolerance (OI)?
Orthostasis means standing upright. So orthostatic intolerance (OI) is the medical term for problems and symptoms that occur when people stand up, or try to remain in a standing position for more than a short period of time. OI is the main reason why most people with ME/CFS try to avoid situations that involve standing still for any period of time.
Consequently, sitting in a chair or sitting up whilst lying on a settee or bed is often the most comfortable position to be in. Orthostatic intolerance is something that affects almost everyone with ME/CFS to some degree and it’s a key diagnostic feature of ME/CFS. For some people, orthostatic intolerance becomes a very disabling part of having ME/CFS. Most of the information and guidance in this leaflet applies to people with ME/CFS who still have some mobility and are able to stand up – even if this is only for a short period of time.
| For people with severe and very severe ME/CFS who are bedbound, changing from having the whole body lying flat to a sitting position in bed can also cause OI symptoms. This needs to be taken into consideration, especially when people with severe ME/CFS have to be admitted to hospital. |
Key Facts
- Orthostasis refers to standing up. So orthostatic intolerance (OI) is the medical term for problems and symptoms that occur when people stand up, or try to remain in a standing position for more than a short period of time.
- OI can also include orthostatic hypotension (where there is a fall in blood pressure on standing) and PoTS/postural orthostatic tachycardia syndrome (a rise in heart rate on standing)
- OI is nearly always exacerbated by anything that diverts blood flow away from the brain.
- OI is probably caused by a problem with the autonomic nervous system – a part of the nervous system that isn’t under conscious control and automatically helps to control heart rate, blood pressure and blood flow to the brain. Problems with balance and muscle weakness in the legs can also play a role.
- There are a number of self-help measures that may be helpful.
- Drugs are sometimes prescribed, especially when OI occurs in association with orthostatic hypotension or PoTS.
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Further information
- 2021 NICE Guideline on ME/CFS: 1.12.9 recommendations on Orthostatic Intolerance | October 2021
- The ME Association Leaflet: Postural Orthostatic Tachycardia Syndrome | Feb 2020