Many people confuse “chronic fatigue” (which is a symptom of many chronic conditions, including rheumatoid arthritis, fibromyalgia, or lupus) or “general tiredness” (which is lifestyle-related), with the specific illness “chronic fatigue syndrome” (ME/CFS). To clarify the differences, here are some of the major symptoms of ME/CFS:

- unexplained physical and mental fatigue for an extended period of time
- post-exertional malaise (meaning an inappropriate loss of physical and mental stamina and a worsening of symptoms after any effort)
- sleep dysfunction
- pain
- neurological/cognitive manifestations
- autonomic manifestations, such as orthostatic intolerance
- neuroendocrine symptoms, such as subnormal body temperature
- immune system changes, such as recurrent flu-like symptoms.