Dark Yellow-Brown Phlegm: Causes, Red Flags & When to See a Doctor

Coughing up dark yellow-brown mucus (sputum) as a non-smoker warrants prompt medical evaluation. Color indicates inflammatory cells, breakdown products, or old blood.

Common Causes

1. Respiratory infections: Bronchitis, pneumonia — neutrophils, debris color mucus
2. Sinusitis: Post-nasal drip of thick, discolored secretions
3. Allergic rhinitis: Eosinophilic inflammation → thick, colored mucus
4. GERD: Acid reflux → airway irritation → mucus production
5. Chronic lung disease: COPD, bronchiectasis, cystic fibrosis — chronic inflammation
6. Environmental: Pollution, dust, smoke exposure

Red Flags (Urgent Evaluation)

• Hemoptysis: Bright red or coffee-ground blood
• Weight loss, night sweats, fever >1 week
• Dyspnea, chest pain
• Risk factors: Immunosuppression, asbestos, TB exposure, travel
• Persistent >3 weeks despite treatment

Potentially Serious Causes

• Lung cancer (especially if >40, smoker history, weight loss)
• TB (night sweats, weight loss, hemoptysis)
• Fungal infection (endemic areas)
• Bronchiectasis (chronic productive cough)
• Pulmonary embolism (sudden dyspnea, pleuritic pain, hemoptysis)

Diagnostic Approach

• Chest X-ray → CT if indicated
• Sputum culture, Gram stain, AFB, cytology
• Pulmonary function tests
• Bronchoscopy if mass/hemoptysis

Do not self-diagnose. Dark sputum in a non-smoker always deserves professional assessment.