Fatigue is one of the most common symptoms people live with — and one of the most misunderstood. When exhaustion persists despite rest, nutrition, and reduced stress, it stops being a lifestyle issue and becomes a medical question.

Clinicians distinguish normal tiredness from pathological fatigue by duration, severity, and impact on daily functioning. Persistent fatigue lasting weeks or months suggests underlying physiological, psychological, or systemic causes.

Why rest does not fix medical fatigue

Medical fatigue is driven by disrupted energy production, chronic inflammation, hormonal imbalance, sleep disorders, mental health conditions, or undiagnosed disease. In these cases, rest alone cannot correct the underlying mechanism.

Common medical causes of persistent fatigue

• Anaemia and nutritional deficiencies
• Thyroid disorders
• Sleep apnoea and sleep fragmentation
• Depression and anxiety
• Chronic infections or inflammatory disease
• Early metabolic or cardiac disease

Red flags that fatigue needs evaluation

• Fatigue lasting longer than 4–6 weeks
• Unintentional weight loss
• Shortness of breath or chest discomfort
• Fever or night sweats
• Reduced ability to work or function

Why fatigue is often dismissed

Because fatigue is subjective and invisible, it is frequently minimised by both patients and clinicians. This delay can allow treatable conditions to progress.

Bottom line: Persistent fatigue is not laziness, ageing, or weakness. It is information — and it deserves investigation.