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Understanding Fatigue: Common Causes and Solutions

Fatigue vs. Sleepiness

Fatigue: overwhelming lack of energy, not relieved by rest. Sleepiness: drive for sleep. Distinct but overlapping.

Major Etiologic Categories

CategoryKey CausesClues
Sleep DisordersOSA, insomnia, circadian rhythm disorders, narcolepsy, insufficient sleep syndromeSnoring, witnessed apneas, unrefreshing sleep, shift work
MedicalAnemia, thyroid (hypo/hyper), diabetes, heart failure, COPD, CKD, liver disease, cancer, chronic infection (TB, HIV, EBV), autoimmune (SLE, RA, MS), POTSAssociated symptoms, abnormal labs/imaging
Medication/SubstanceBeta-blockers, antihistamines, opioids, benzos, antidepressants, antipsychotics, alcohol, cannabis, stimulant withdrawalTemporal relationship to start/dose change
PsychiatricDepression (fatigue ≠ sadness), anxiety, PTSD, grief, burnoutAnhedonia, worry, trauma cues, work exhaustion
NutritionalIron, B12, folate, vitamin D, magnesium, potassium deficiency; dehydrationDiet history, labs
LifestyleSedentary, erratic schedule, caffeine/alcohol timing, poor sleep hygieneImproves with structure
EndocrineAdrenal insufficiency, hypogonadism, growth hormone deficiencySpecific hormone deficits
NeurologicMS, Parkinson’s, TBI, post-concussion, CFS/MENeuro signs, post-exertional malaise (PEM)

Diagnostic Approach

  1. History: onset, pattern, alleviating/aggravating, sleep log, review of systems, medications, psychosocial.
  2. Physical: vitals, BMI, thyroid, lymph, cardiac, pulmonary, neuro, skin.
  3. Initial labs: CBC, CMP, TSH, free T4, ferritin, B12, folate, vitamin D, HbA1c, ESR/CRP, UA.
  4. Targeted: Sleep study, CPET, tilt table, autoantibodies, hormones, imaging per suspicion.
  5. Diagnosis of exclusion: CFS/ME (IOM criteria), fibromyalgia, idiopathic chronic fatigue.

Management Principles

  • Treat identifiable cause (e.g., CPAP for OSA, iron for IDA, levothyroxine for hypothyroidism).
  • Graded exercise therapy (GET) for deconditioning/CFS (controversial; pace, don’t push).
  • Cognitive-behavioral therapy (CBT-I for insomnia, CBT-F for fatigue).
  • Energy conservation: Pacing, prioritization, delegation (spoon theory).
  • Sleep hygiene: Fixed rise time, light exposure, caffeine cutoff 12 pm, wind-down routine.
  • Medication review: Deprescribe sedating drugs if possible.
  • Stimulants (modafinil, methylphenidate): Residual sleepiness in OSA, MS, depression – specialist only.

Red Flags for Urgent Evaluation

  • Weight loss, fever, night sweats, lymphadenopathy.
  • New neurologic deficits.
  • Chest pain, dyspnea, palpitations.
  • Suicidal ideation.

Fatigue is a symptom, not a diagnosis. Systematic evaluation yields treatable causes in >50% of cases.

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