Doctor Warns: Dark Stool May Signal Internal Bleeding
A doctor warns that tar-like black stools may signal dangerous upper digestive bleeding rather than diet, especially when accompanied by dizziness or weakness, and urges immediate medical evaluation in such cases.
Dr. Jedsada Bunyavongvirot, deputy director of primary care at Maha Sarakham Hospital, posted on social media warning people not to dismiss dark stools. He explains that while a single dark stool often leads people to ask "Did I eat something black yesterday?" or "Did I eat pork blood?" the cause is not always dietary.
When stool is jet black, sticky, glossy, resembles tar, and has an unusually foul odor, it may indicate melena—bleeding in the upper digestive tract from the stomach or small intestine. The blood is digested as it travels downward, turning black. Evaluation requires considering color, texture, odor, accompanying symptoms, and current medications or supplements.
If stool appears tar-like, bleeding should be suspected first. Such stools are typically jet black, sticky, glossy, and difficult to wipe away, often with a strong, distinctly foul smell caused by digestive acids breaking down blood. Common causes include gastric ulcers, duodenal ulcers, severe gastritis, ruptured blood vessels in the esophagus or stomach, and certain cancers or medications. If this occurs repeatedly, medical evaluation is essential.
If stool is dark but not sticky, glossy, or foul-smelling, it may come from food or medication rather than bleeding. Iron supplements, certain bismuth-containing medicines, dark foods, pork blood, and some supplements can darken stool. If darkening began after starting iron supplements with no other symptoms, medication may be the cause. However, if dizziness, paleness, heart palpitations, or weakness accompany dark stool, blood loss should be suspected.
Dark stool combined with dizziness, heart palpitations, or fainting requires urgent evaluation—significant bleeding can cause blood volume loss affecting blood pressure and circulation. Associated symptoms include dizziness, lightheadedness upon standing, rapid heartbeat, severe weakness, pallor, sweating, rapid breathing, or fainting. If these accompany dark stool, home observation is not recommended, as concern extends beyond stool color to whether blood loss is affecting circulation. Vomiting blood or coffee-ground-colored vomit requires immediate medical assessment.
People taking pain relievers or blood thinners must be especially cautious. Those with dark stools should be asked about medications immediately, particularly NSAIDs like ibuprofen, diclofenac, and naproxen, which increase risk of gastric or intestinal ulcers and bleeding, especially with frequent or high-dose use or combined with other medications.
Antiplatelet and anticoagulant drugs like aspirin, clopidogrel, warfarin, and DOACs also require consideration, though such medications are not inherently "bad."
