Why does gastritis cause black stools?

Blood exposed to stomach acid and digestive enzymes darkens, so the stool may look black, sticky, or tar-like rather than red. Black stools are a common presentation of gastritis, but they can also come from bleeding elsewhere in the upper digestive tract or from non-bleeding causes.

Gastritis is inflammation of the stomach lining. When that lining is irritated enough to bleed, the blood changes colour before leaving the body. A black stool linked to bleeding often has a strong, unusual smell and a tarry texture. Iron supplements, bismuth-containing stomach medicines, and some foods can also darken stool without causing bleeding.

The appearance alone cannot confirm the cause. A clinician may consider your medicines, recent symptoms, and signs of blood loss, then decide whether testing or a closer look at the upper digestive tract is appropriate.

Arrange prompt medical advice for a new black or tarry stool, especially if you have upper abdominal pain, nausea, vomiting, or feel unusually tired. Tell the clinician about anti-inflammatory pain medicines, aspirin, blood-thinning medicines, iron, and bismuth products, because these details can affect both the cause and the next steps.

Do not stop a prescribed blood thinner on your own. Avoid alcohol and avoid taking extra anti-inflammatory pain medicine unless a clinician who knows your situation advises it. Keep note of when the colour started and whether it recurs.

Seek urgent medical care now if black stools occur with fainting, dizziness, weakness, shortness of breath, confusion, severe abdominal pain, vomiting blood, or vomit that resembles coffee grounds. These symptoms can signal substantial bleeding or reduced blood flow and need rapid assessment.

Even without these warning signs, repeated black tarry stools should be assessed promptly. Passing black stool after taking iron or bismuth may be harmless, but it is still worth checking if the change is new, persistent, or accompanied by stomach symptoms.

Ask whether your stool appearance could be from bleeding, medicine, or food; whether any current medicine could irritate the stomach lining; and whether you need blood tests or an examination of the stomach. Bring a complete list of prescribed, over-the-counter, and herbal products.