Diverticulitis and black stool: what should you know?

Diverticular disease can be associated with bowel bleeding, but black, tar-like stool can also result when blood has travelled through the upper digestive tract. Iron tablets, bismuth medicines and some foods can darken stool without bleeding, yet appearance alone cannot safely distinguish the causes. Abdominal pain, weakness, dizziness, vomiting blood or a fast heartbeat makes the situation more concerning.

Contact a medical service promptly and describe the colour, texture, timing and amount, along with any pain or medicines. Do not take anti-inflammatory painkillers or stop prescribed medicines without advice. Keep hydrated only if you can drink normally, and avoid driving yourself if you feel faint or weak. A GP assessment can review medicines and decide whether urgent tests are needed.

Call emergency services or attend an emergency department for black stool with faintness, confusion, severe weakness, breathlessness, severe abdominal pain, vomiting blood, a cold clammy feeling or ongoing bleeding. Treat this as urgent even if you have previously been told you have diverticular disease. Do not wait to see whether the next bowel movement looks different.

Ask whether your medicines or supplements can darken stool, whether bleeding needs testing, which pain relief is safe, and what symptoms should trigger emergency care.