What causes dark green diarrhea?

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Last updated: June 8, 2025View editorial policy

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From the Guidelines

Dark green diarrhea is typically caused by bile pigments moving too quickly through the digestive system, not allowing them to be properly broken down, and can be a result of various factors including certain foods, medications, and underlying medical conditions. The most common causes of dark green diarrhea include:

  • Certain foods like leafy greens, food coloring, and iron supplements
  • Medications such as antibiotics
  • Medical conditions like infections (bacterial, viral, or parasitic), inflammatory bowel disease, irritable bowel syndrome, and malabsorption disorders According to the study by 1, the green color comes from biliverdin, a bile pigment that normally gets converted to brown in the intestines during slower digestion. When diarrhea speeds up intestinal transit time, this conversion doesn't fully occur, resulting in green stool. Some key points to consider:
  • Persistent symptoms, especially when accompanied by fever, severe abdominal pain, blood in stool, or dehydration, warrant medical attention
  • Treatment typically addresses the underlying cause, whether that's discontinuing certain supplements, treating infections with appropriate medications, or managing chronic digestive conditions
  • Infections such as Clostridium difficile, as discussed in the study by 1, can also cause diarrhea and should be considered in the diagnosis
  • Other bacterial infections like nontyphoidal Salmonella, Shigella, Yersinia, or Campylobacter spp. can also cause diarrhea, as mentioned in the study by 1 It's essential to note that while occasional green diarrhea isn't usually concerning, it's crucial to seek medical attention if symptoms persist or worsen over time.

From the Research

Causes of Dark Green Diarrhea

  • The exact cause of dark green diarrhea is not explicitly stated in the provided studies, however, several factors can contribute to the occurrence of diarrhea, including:
    • Gut microbiota dysbiosis, which can be caused by infections, antibiotics, or other factors 2, 3
    • Pathogen infections, such as viral, bacterial, or parasitic species, which can alter the gut microbiome and lead to diarrhea 3
    • Abiotic factors, such as childhood malnutrition, which can have negative influences on the gut microbiota 3
  • The color of diarrhea can be influenced by various factors, including:
    • The presence of certain bacteria or viruses in the gut microbiome
    • The type of food consumed, which can affect the composition of the gut microbiome and its metabolites 4
    • The level of gut inflammation or infection, which can cause changes in the color and consistency of stool

Role of Gut Microbiota in Diarrhea

  • The gut microbiota plays a crucial role in the development and treatment of diarrhea, with dysbiosis contributing to the occurrence of diarrhea 2, 3
  • Reprograming gut microbiota communities through dietary probiotics or fecal bacteria transplantation can help treat or prevent diarrhea 2
  • The composition of the gut microbiome is influenced by the host's diet, with dietary fibers acting as prebiotics and certain bacterial species supporting the host's wellbeing as probiotics 4

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Gut Microbiota and Diarrhea: An Updated Review.

Frontiers in cellular and infection microbiology, 2021

Research

Diarrheal disease and gut microbiome.

Progress in molecular biology and translational science, 2022

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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