Chronic Condition

Chronic Fatigue Syndrome (ME/CFS) — Symptoms & Diagnosis

What ME/CFS is, the key symptom of post-exertional malaise, and which blood tests are ordered to investigate fatigue.

Key feature
Post-exertional malaise (PEM)
Duration for diagnosis
> 6 months
Blood tests
Normal in most

What Is ME/CFS?

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex, chronic illness characterised by profound, disabling fatigue that is not relieved by rest. It is not psychological — emerging research points to immune dysregulation, autonomic dysfunction and energy metabolism problems.

Core Symptoms

Blood Tests — Ruling Out Other Causes

TestCondition Ruled Out
TSH, Free T4Hypothyroidism or hyperthyroidism
Full Blood CountAnaemia, infection, blood disorders
ESR & CRPInflammatory conditions
ANALupus
Vitamin B12 & FolateDeficiency states
Vitamin DDeficiency (very common in fatigue)
Fasting Glucose + HbA1cDiabetes
Liver & Kidney functionOrgan disease
CalciumHyperparathyroidism
Cortisol (9am)Adrenal insufficiency

Post-COVID and ME/CFS

Long COVID shares significant overlap with ME/CFS — particularly PEM, fatigue, brain fog and autonomic dysfunction. Many long COVID patients meet criteria for ME/CFS.

Management

FAQs

Is ME/CFS treatable?
There is no cure, but management can significantly reduce symptom burden. Pacing is the most evidence-supported approach for preventing deterioration.
Why does exercise make ME/CFS worse?
PEM — post-exertional malaise — is a hallmark feature. Aerobic exercise appropriate for deconditioning can be harmful in ME/CFS; pacing is recommended instead.
Is ME/CFS recognised by major health bodies?
Yes — the WHO, NHS, CDC and NIH all recognise ME/CFS as a serious chronic disease with ongoing research into its mechanisms.
Medical Disclaimer: ME/CFS diagnosis requires exclusion of other treatable conditions. Management should be with a doctor familiar with the condition.