Coughing Up Dark Brown Phlegm: Causes & When to Worry

Dark brown sputum suggests old blood or inhaled particulates. Common causes:

1. Smoking: Tar, nicotine, and chronic bronchitis → brown/black mucus.
2. Air pollution/dust: Occupational (coal, silica) or environmental.
3. Chronic bronchitis: Productive cough ≥3 mo/yr × 2 yrs; mucus often brownish.
4. Pneumonia: Rust-colored (pneumococcal) or dark brown (anaerobic, aspiration).
5. Bronchiectasis: Thick, tenacious, often foul-smelling brown/green sputum.
6. Tuberculosis: Blood-tinged to brown; night sweats, weight loss.
7. Lung cancer: Hemoptysis (blood) may darken over time.
8. Pulmonary embolism (rare): Infarction → bloody/brown sputum.
9. Medications: Amiodarone, rifampin can discolor secretions.

Red Flags: Urgent Evaluation

• Hemoptysis (bright red or coffee-ground).
• Weight loss, night sweats, fever >1 week.
• Shortness of breath, chest pain.
• Smoker >40 pack-years or new cough >3 weeks.

Diagnostic Steps

• Chest X-ray → CT if abnormal.
• Sputum culture, AFB, cytology.
• Bronchoscopy if mass suspected or hemoptysis.

Don’t ignore persistent dark phlegm—early diagnosis of TB, cancer, or bronchiectasis changes outcomes.