# Chronic Fatigue Syndrome > Chronic fatigue syndrome for NEET-PG Medicine: ME/CFS diagnostic criteria, post-exertional malaise, graded exercise controversy and NICE 2021. - Canonical URL: https://prepelephant.com/topics/neet-pg/medicine/chronic-fatigue-syndrome - Exam / course: NEET-PG · Subject: Medicine - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Chronic Fatigue Syndrome", PrepElephant, https://prepelephant.com/topics/neet-pg/medicine/chronic-fatigue-syndrome ## Direct answer Chronic fatigue syndrome, also called myalgic encephalomyelitis or systemic exertion intolerance disease, is diagnosed clinically after exclusion: at least six months of substantially activity-limiting fatigue not relieved by rest, with post-exertional malaise — a disproportionate worsening after previously trivial exertion — plus unrefreshing sleep and either cognitive impairment or orthostatic intolerance, per the 2015 Institute of Medicine criteria. There is no diagnostic test and no curative drug; management is energy management with pacing, individualised symptom treatment for pain and sleep, and a cautious, monitored return of activity that never exceeds the patient's envelope, since 2021 National Institute for Health and Care Excellence guidance withdrew graded exercise therapy as a default recommendation. In India the diagnosis is often delayed because the differential — anaemia, hypothyroidism, tuberculosis, depression, diabetes — must first be excluded and re-examined, and because post-viral fatigue clinics barely exist outside major centres. ## What you must remember - **Core diagnostic triad:** six months or more of medically unexplained, activity-limiting fatigue; post-exertional malaise; and unrefreshing sleep — with cognitive dysfunction ("brain fog") or orthostatic intolerance completing the criteria set. - **Exclusion screen before labelling:** full blood count, erythrocyte sedimentation rate or C-reactive protein, thyroid-stimulating hormone, fasting glucose, electrolytes, creatinine, liver tests, human immunodeficiency virus and hepatitis serology where indicated, and a drug and alcohol history — the diagnosis is one of exclusion and follow-up. - **What it is not:** fatigue explained by anaemia, hypothyroidism, sleep apnoea, depression, tuberculosis or malignancy — and the exam expects you to name the screen rather than accept the label at face value. - **Pacing over pushing:** energy management keeps expenditure within limits, plans rest before crashes and avoids the boom-bust cycle; per the 2021 NICE guideline, graded exercise therapy is no longer offered routinely and cognitive behavioural therapy is supportive, not curative. - **Overlap territory:** a substantial proportion report onset after viral infection — dengue, chikungunya, Epstein-Barr and notably post-coronavirus disease states share the post-exertional malaise phenotype, making the criteria newly relevant in Indian practice. - **Comorbidities to treat in their own right:** fibromyalgia-type widespread pain, irritable bowel syndrome, orthostatic intolerance including postural orthostatic tachycardia syndrome, and depression or anxiety — each treated on its own evidence. - **Red flags redirecting the workup:** weight loss, fever, lymphadenopathy, focal neurological signs, raised inflammatory markers — these are not chronic fatigue syndrome and reopen the search. ## A typical clinic case A 34-year-old teacher presents with ten months of exhaustion after a documented dengue infection; she sleeps twelve hours and wakes unrefreshed, and a supermarket trip confines her to bed for two days. The reasoning runs in three moves. First, exclude with the screen above plus a tilt-standing bedside test for orthostatic vitals — all normal, repeated once, Second, apply the criteria: duration well past six months, activity substantially reduced, unmistakable post-exertional malaise, unrefreshing sleep and concentration difficulty — the clinical box is ticked and she is told the diagnosis explicitly, because naming the illness reduces iatrogenic harm. Third, manage: pacing diary with her worst-day baseline, sleep hygiene without sedative dependence, low-dose symptomatic treatment for myalgia, a planned workplace accommodation letter, and scheduled review every few months to re-examine and catch any evolving alternative diagnosis. The case teaches the shape of good care — exclusion, explanation, envelope-based rehabilitation, vigilance — in a condition with no single decisive test. ## Where students slip Two errors dominate. The first is treating the label as a diagnosis of exclusion so aggressive that the patient is investigated for years and never told what they have — the criteria are clinical and positive once the screen is clean, and delayed naming is itself harmful. The second is reflexively prescribing graded exercise: the exam-aware answer reflects the 2021 NICE position that therapy must be individualised, malaise-monitored and never a fixed escalating protocol, because post-exertional worsening is the defining symptom. A third, quieter slip is conflating chronic fatigue syndrome with depression — the discrimination lies in anhedonia and mood change dominating depression, while effort-triggered physical deterioration and unrefreshing sleep dominate chronic fatigue syndrome, though they coexist often enough that both need treating. ## Frequently asked questions ### What are the Institute of Medicine criteria for chronic fatigue syndrome? Six months of substantial activity-limiting fatigue with post-exertional malaise and unrefreshing sleep, plus cognitive impairment or orthostatic intolerance, after excluding alternatives. ### Which investigations precede the diagnosis? Full blood count, inflammatory markers, thyroid-stimulating hormone, glucose, renal and liver biochemistry, and where indicated human immunodeficiency virus and hepatitis serology — a defined exclusion screen. ### What changed in the 2021 NICE guideline? Graded exercise therapy was withdrawn as a routine recommendation; energy management with pacing, delivered individually and monitored for post-exertional worsening, became the core approach. ### What is post-exertional malaise? Disproportionate deterioration in symptoms — exhaustion, cognitive fog, myalgia — beginning hours to a day after exertion that the patient previously tolerated, lasting days. ### How is chronic fatigue syndrome distinguished from depression? Depression leads with anhedonia, guilt and mood change; chronic fatigue syndrome leads with effort-triggered physical deterioration and unrefreshing sleep — though comorbidity is common and both are treated.