Because there is no accepted test for this condition, ME/CFS is diagnosed by exclusion. What this means is that the condition is diagnosed by first excluding all other diseases that are similar to ME/CFS. This typically requires tests for anemia, thyroid conditions, mononucleosis, depression, Lyme disease, diabetes, multiple sclerosis, cancers, and bipolar disorder. Once these other diseases have been ruled out, then the diagnosis of ME/CFS is made based on symptoms.
The diagnostic criteria most often used are described in the 1994 International ("Fukuda") Definition for Chronic Fatigue Syndrome. According to that definition, a person is considered to have ME/CFS if he/she has:
1. Unexplained, persistent or relapsing chronic fatigue that is not substantially alleviated by rest, and results in substantial reductions in levels of occupational, educational, social, or personal activities; and
2. Four or more of the following symptoms lasting for six or more consecutive months:
- Self-reported impairment in short-term memory or concentration
- Post-exertional malaise (extreme, prolonged exhaustion and a worsening of symptoms following physical or mental exertion)
- Unrefreshing sleep
- Muscle pain Multi-joint pain without joint swelling or redness
- Sore throat Tender neck lymph nodes
- Headaches of a new type, pattern, or severity
