What should you know about black green stool in adults?

For adults, recent changes in diet or supplements are useful clues. Iron can make stool very dark, while green foods, colouring and bile can add a green cast. Stool from bleeding higher in the digestive tract is often black and tar-like rather than simply dark brown. Gastritis, Helicobacter pylori infection and peptic ulcer can be associated with upper digestive symptoms and bleeding, but a clinician must assess the whole pattern rather than colour alone.

Review what changed before the stool appeared, including supplements, pain medicines and foods. Note whether the stool is formed, loose, sticky or difficult to flush. Seek medical advice when the colour has no clear explanation, keeps returning, or occurs with stomach symptoms. Bring a medication list to the appointment.

Adults should seek urgent help for tarry stool, vomiting blood, fainting, severe or worsening abdominal pain, marked weakness, breathlessness or a rapid heartbeat. These signs may indicate blood loss and should not be monitored at home.

Ask whether the colour could be medication-related, whether an ulcer or stomach inflammation needs checking, and what warning signs require emergency review. Describe the first episode and any change in frequency or texture.