What are the key diagnostic criteria for Chronic Fatigue Syndrome (ME/CFS) according to current UK guidelines?

Guideline-aligned answer with reasoning, red flags and references. Clinically reviewed by Dr Kola Tytler MBBS CertHE MBA MRCGP.

Posted: 16 August 2025Updated: 16 August 2025 Guideline-Aligned (High Confidence) Clinically Reviewed
Dr Kola Tytler MBBS CertHE MBA MRCGPClinical Lead • iatroX

Suspect ME/CFS if: the person has had all of the persistent symptoms in box 2 for a minimum of 6 weeks in adults and 4 weeks in children and young people .

All of these symptoms should be present: debilitating fatigue that is worsened by activity, is not caused by excessive exertion, and is not significantly relieved by rest; post-exertional malaise with delayed onset, disproportionate worsening, and prolonged recovery; unrefreshing sleep or sleep disturbance; and cognitive difficulties such as problems with word-finding, memory, and concentration .

Symptoms should significantly reduce the person's ability to engage in occupational, educational, social, or personal activities .

Related Knowledge Topics

Educational content only. Always verify information and use clinical judgement.