VHOSPITAL.CLINIC · Medical Q&A

What Causes Black tarry stools?

A complete overview of all potential causes of melena, from benign to serious medical conditions.

What It Means

Black tarry stools has many potential causes spanning multiple organ systems. A systematic approach — considering the character, timing, triggers, and associated symptoms — helps identify the most likely cause and guides appropriate management.

Common Causes

  • Infectious causes: viral, bacterial, or fungal pathogens triggering systemic or localised melena
  • Inflammatory/autoimmune: the body's immune response producing melena as a bystander effect
  • Metabolic: disorders of thyroid, adrenal, or blood glucose regulation
  • Structural/mechanical: nerve compression, joint damage, or organ enlargement
  • Underlying conditions: various medical conditions are among the leading identifiable causes

Red Flags — When to Act

  • Unintentional weight loss accompanying melena (possible malignancy or metabolic disease)
  • Night sweats, fever, and melena persisting >2 weeks
  • New melena in someone with a known cancer, immunosuppression, or recent surgery
  • Rapid progression or change in the character of long-standing melena
  • Family history of serious hereditary conditions presenting with melena

What to Do Now

  1. 1.Keep a symptom diary: date, time, severity, triggers, and what improves or worsens melena
  2. 2.Review your medications — many drugs can cause melena as a side effect
  3. 3.Assess lifestyle factors: sleep, diet, alcohol, exercise, and hydration
  4. 4.Use our AI symptom checker to receive a structured differential and guidance
  5. 5.Book a GP appointment for persistent, recurring, or unexplained melena

When to See a Doctor

  • Black tarry stools persists beyond 1 week without an obvious cause
  • Severity is moderate-to-severe or worsening over time
  • Any red-flag features are present (see above)

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Frequently Asked Questions

What is the most common cause of melena?

The most common causes of melena in the general population are stress, dehydration, poor sleep, and minor infections. In specific populations, chronic disease and other underlying conditions account for a significant proportion of cases.

Can medications cause melena?

Yes — many medications list melena as a potential side effect. Common culprits include antihypertensives, antibiotics, NSAIDs, and hormonal treatments. Review your medication list with a pharmacist or doctor if you suspect a drug-related cause.

Is melena always related to a physical cause?

No. Psychological conditions such as anxiety, depression, and stress disorders frequently produce genuine physical melena through the mind-body axis. Psychosomatic melena is a real, measurable phenomenon requiring appropriate treatment.

Related Resources

Possible Causes

  • Infectious causes: viral, bacterial, or fungal pathogens triggering systemic or localised melena
  • Inflammatory/autoimmune: the body's immune response producing melena as a bystander effect
  • Metabolic: disorders of thyroid, adrenal, or blood glucose regulation
  • Structural/mechanical: nerve compression, joint damage, or organ enlargement
melenaFull symptom guide

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Medical ReviewvHospital Editorial Team · 2024–2025
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