Consider a diagnosis of CFS if these three criteria are met:

1. The individual has severe chronic fatigue for ≥6 consecutive months that is not due to ongoing exertion or other medical conditions associated with fatigue (these other conditions need to be ruled out by a doctor after diagnostic tests have been conducted)
2. The fatigue significantly interferes with daily activities and work.
3. The individual concurrently has four or more of the following eight symptoms:
   • postexertion malaise lasting >24 hours
   • unrefreshing sleep
   • significant impairment of short-term memory or concentration
   • muscle pain
   • multijoint pain without swelling or redness
   • headaches of a new type, pattern, or severity
   • tender cervical or axillary lymph nodes
   • sore throat that is frequent or recurring