Tiredness/fatigue in adults
Exam Tips
- In OSCE history, characterise fatigue precisely (onset, duration, fluctuation, exertional pattern, sleep effect, and functional impact) before jumping to diagnosis.
- Always ask about daytime somnolence, snoring, witnessed apnoeas, and sedative medication use; these are high-yield reversible causes.
- Red flags to actively screen: weight loss, persistent fever/night sweats, lymphadenopathy, focal neurological deficit, cardiorespiratory symptoms, and bleeding.
- Differentiate true muscle weakness from subjective tiredness; objective proximal weakness points to neuromuscular/endocrine pathology.
- A focused first-line blood panel (FBC, ferritin, CRP/ESR, U&E, LFT, TFT, HbA1c) is commonly expected in UK exam answers when no focal diagnosis is obvious.
- When discussing management, state: no routine stimulant therapy for unexplained fatigue; treat the confirmed cause, optimise sleep/activity, and provide safety-net follow-up.
Definition
Tiredness/fatigue in adults is a common, subjective, non-specific symptom characterised by reduced physical and/or mental energy that impairs usual functioning. It is not a single diagnosis, but a clinical presentation that may reflect physiological strain, psychosocial distress, medication effects, or underlying medical disease. In practice, fatigue ranges from transient self-limiting tiredness to persistent disabling symptoms requiring targeted investigation.
Pathophysiology
Fatigue is multifactorial and arises when energy supply, sleep-wake regulation, neuromuscular function, and cognitive-emotional processing are disrupted. Peripheral mechanisms include impaired oxygen delivery (for example anaemia), endocrine/metabolic dysfunction (for example hypothyroidism, diabetes), inflammatory cytokine signalling after infection, and cardiorespiratory or renal/hepatic disease reducing tissue performance. Central mechanisms include altered arousal networks, circadian misalignment (notably shift work), mood disorders, chronic stress, pain, and sedative or centrally acting drugs (including first-generation antihistamines), which reduce alertness, motivation, concentration, and perceived effort.
Risk Factors
- Female sex
- Chronic medical comorbidity (including cardiorespiratory, renal, liver, autoimmune/rheumatological disease, chronic pain)
- Psychosocial morbidity (depression, anxiety, stress, bereavement, burnout, adjustment reactions)
- Shift work/circadian disruption and poor sleep hygiene
- Low physical activity, prolonged sedentary time, and higher BMI
- Lower socioeconomic and educational status
- Medication/substance contributors (benzodiazepines, antidepressants, sedating antihistamines, beta-blockers, opioids, recreational drugs, nicotine)
Clinical Features
Symptoms
- Persistent tiredness, low energy, exhaustion, or early fatigability
- Daytime sleepiness or tendency to fall asleep (consider sleep apnoea/sleep disorder)
- Unrefreshing sleep or sleep disturbance
- Reduced exercise tolerance and post-activity worsening
- Cognitive slowing, poor concentration, memory lapses ('brain fog')
- Associated mood symptoms (anxiety, low mood, anhedonia), stress, or burnout
- Functional impact on work/education, driving safety, relationships, and activities of daily living
Signs
- Often non-specific or normal examination
- Pallor (possible anaemia/malignancy), lymphadenopathy (infection/malignancy)
- Goitre or thyroid signs
- Abnormal pulse/rhythm, murmur, oedema, postural hypotension
- Neurological deficit or objective muscle weakness suggesting neuromuscular/neurological disease
- BMI/nutritional abnormalities and weight change
- Mental state abnormalities (depressed affect, anxiety, cognitive impairment)
Investigations
Management
Lifestyle Modifications
- Validate symptoms and explain uncertainty early; use shared plan with safety-netting
- Address sleep hygiene and circadian factors; optimise shift-work scheduling where possible
- Graded return to activity with pacing (avoid boom-bust overexertion)
- Review diet, hydration, alcohol, nicotine, and recreational drug use
- Assess psychosocial stressors, carer burden, occupational risks, and driving safety
- Arrange follow-up to review evolution, test results, and red flags
Pharmacological Treatment
Medication review and iatrogenic causes
- Chlorphenamine 4 mg every 4-6 hours (max 24 mg/day) - consider withdrawal/switch if daytime sedation
- Loratadine 10 mg once daily as a less-sedating antihistamine alternative when allergy treatment is needed
No drug treats unexplained fatigue directly; identify and reduce causative medicines (for example sedating antihistamines, benzodiazepines, opioids, some antidepressants/beta-blockers). Sedating antihistamines and other CNS depressants impair driving/operating machinery; advise explicitly.
Treat confirmed iron deficiency anaemia
- Ferrous sulfate 200 mg oral tablet once daily (contains ~65 mg elemental iron), continue about 3 months after Hb normalises
Common adverse effects: constipation, nausea, abdominal pain, dark stools. Absorption reduced by antacids/calcium; separate dosing. Do not give empirically without evidence of deficiency; investigate cause of iron deficiency (including GI blood loss in at-risk adults).
Treat confirmed hypothyroidism
- Levothyroxine sodium typically 50-100 micrograms once daily, titrated to TSH (start lower, e. g. 25 micrograms daily, in older adults or ischaemic heart disease)
Avoid overtreatment (risk of atrial fibrillation/osteoporosis). Check adherence and interactions (iron/calcium reduce absorption; separate administration).
Treat confirmed vitamin B12 deficiency
- Hydroxocobalamin 1 mg intramuscularly three times weekly for 2 weeks, then maintenance 1 mg every 2-3 months if non-dietary cause
If neurological involvement, use more intensive initial regimen per local protocol and urgent specialist input. Do not delay treatment when neurological deficits are present.
Treat comorbid depression/anxiety when diagnosed
- Sertraline 50 mg once daily, increase gradually up to 200 mg once daily if needed
Discuss early adverse effects, suicidality monitoring (especially younger adults), and withdrawal effects. Use alongside psychological interventions; not all fatigue with low mood requires immediate antidepressant therapy.
Complications
- Reduced quality of life and impaired social/occupational functioning
- Cognitive impairment with reduced attention, slower processing, and memory lapses
- Increased workplace errors, accidents, and injury risk (including machine-paced/complex work)
- Road traffic collision risk from fatigue-related inattention/somnolence
- Emotional sequelae including loss of motivation, anxiety, and depression
- Poorer adherence and outcomes in comorbid chronic disease
Prognosis
In primary care, many cases improve spontaneously and most patients do not need prolonged follow-up. Around one-third to one-half recover within a year, with better outcomes linked to shorter symptom duration, lower initial severity, better general/mental health, lower pain burden, and good social support. Persistent fatigue is more likely when symptoms are severe, prolonged, and accompanied by significant psychosocial or medical comorbidity.
Sources & References
✅NICE Guidelines(1)
- Tiredness/fatigue in adults[overview]
📖Textbook References(2)
- Guyton and Hall Textbook of Medical Physiology (John E. Hall, Michael E. Hall) (Z-Library).pdf(pp. 100, 101)[context]
- Netter F. Netter Atlas of Human Anatomy. Classic Regional Approach 8ed 2022.pdf(pp. 290, 291)[context]