What should you know about bismuth black stool?

Bismuth compounds can react with sulphur in the digestive system and darken the stool or tongue. This colour change can happen without blood loss and should fade after the medicine is stopped. Black stool can also result from bleeding higher in the digestive tract, including with gastritis, Helicobacter pylori infection, or a peptic ulcer. Bleeding stool is often sticky or tar-like and may have a strong smell, but colour alone cannot safely identify the cause.

Record when the bismuth was taken, the dose on the label, and when the stool changed. Check for repeated black stools and other symptoms. Take the product only as directed and avoid combining medicines that contain the same ingredient. If the colour persists after the medicine is stopped, or you are unsure whether it is tarry, contact a clinician for advice. Do not use leftover treatment to explain away new symptoms.

Seek urgent care for black tarry stool with dizziness, fainting, weakness, fast heartbeat, vomiting blood, severe abdominal pain, or unusual paleness. Arrange prompt assessment for repeated black stools, especially if you take medicines that increase bleeding risk or have a history of ulcer disease. A clinician may need to examine you and arrange tests.

Does the appearance fit a bismuth colour change or possible bleeding? Should I stop or change the product? Could my other medicines or digestive history raise bleeding risk?