Diagnosis is made when the patient meets all 3 required criteria and has ≥ 1 of the additional criteria:
Required Criteria
1. Fatigue results in a significant reduction or impairment in the patient’s ability to function at the same level of activity prior to illness
✓ Fatigue is new (not life-long)
✓ Lasts for > 6 months
✓ Not just the result of excessive exertion (eg, working out)
✓ Not substantially alleviated by rest
✓ A substantial reduction or impairment in the ability to engage in pre-illness levels of occupational, educational, social, or personal activities
2. Post-exertional malaise*
✓ Increased symptoms after physical, mental, or emotional exertion when engaging in activities that would have been tolerated previously
✓ May occur hours to days after exertion
✓ May last days, weeks, or months
3. Unrefreshing sleep*
✓ Can occur despite a full night of sleep.
Additional Criteria
1. Cognitive impairment*
✓ Can include memory and executive function challenges and “brain fog”
2. Orthostatic intolerance
✓ Worsening symptoms when upright
✓ Lightheaded, increasing fatigue, worsening “brain fog,” fainting
✓ Elevated heart rate, decreased blood pressure when upright
*Symptoms must be moderate to severe and present > 50% of the time
Medscape and CDC