Symptoms of Melena and black stool causes: Here's when you should worry

Causes of black stool: Consuming certain dark foods, such as black licorice, blueberries, or foods with deep colouring, can temporarily darken stool (Images: Canva)

A jet‑black, sticky stool that has a strange odour can be blamed on the previous night’s indulgence, perhaps a dark meal, black tea or pills. But sometimes, that jet‑black stool has a far more serious origin, like, blood that’s been digested as it made its way through your gastrointestinal tract. This condition called Melena is a silent warning sign that something inside may be wrong.

Experts warn that black or tarry stools often indicate bleeding in the upper parts of the digestive system, such as the oesophagus, stomach or first section of the small intestine. Blood that enters the gut from a bleed gets broken down by stomach acid, digestive enzymes and bacteria. As it travels, it darkens and becomes sticky, giving that “tar‑like” appearance and often a foul smell.

Diet and medication

According to the National Institutes of Health (NIH), while diet or medications sometimes cause black stools, consistent, tarry black stool calls for medical evaluation to rule out internal bleeding rather than dismissing it as harmless.

However, not all black stool signals danger. Consuming certain dark foods, such as black licorice, blueberries, or foods with deep colouring, can temporarily darken stool.

Supplements and medications also play a role. Iron supplements, for instance, often turn stool dark, as do medicines containing bismuth (like some antacids and stomach‑soothing drugs). In these benign cases, stool colour typically returns to normal once you stop the supplement or the food passes through, and there are no other worrisome symptoms.

Causes of Melena

Peptic ulcers and gastritis

One of the most frequent causes of Melena is a bleeding ulcer in the stomach or duodenum (first part of small intestine). Chronic inflammation of the stomach lining (gastritis) can also erode tissue and lead to bleeding.

Varices, tears or lesions

Enlarged or swollen veins in the oesophagus or stomach (varices), common in people with liver disease, may rupture and bleed. A tear in the oesophagus (for example after violent vomiting) can also cause bleeding that later shows up as black stool.

Internal trauma, cancer or other diseases

Less commonly, serious conditions such as gastric cancer or other digestive‑tract disorders can trigger slow, often silent bleeding resulting in Melena.

Symptoms of melena

Stool that’s black, sticky or tar-like, frequently described as having a foul odour.

Other signs along with the stool change: weakness, dizziness, rapid heartbeat, pale skin, fatigue, possible signs of blood loss.

Additional symptoms

Abdominal pain, indigestion, vomiting blood (or vomit that looks like coffee‑grounds), or black stool lasting more than one bowel movement. If you notice any of these, especially without a clear dietary or medicinal reason, it’s important to get checked by a doctor.

Diagnosis and treatment

First, a doctor may order a stool test to check for hidden blood. If blood is detected or symptoms suggest internal bleeding, the next step is often endoscopy (a flexible camera inserted via the mouth) to visualise the digestive tract, find ulcers, varices, or lesions, and sometimes treat the cause directly Treatment depends entirely on what’s causing the bleed: ulcers may be treated with acid‑blocking drugs, inflamed tissue with medication, varices with banding or other interventions; significant blood loss may require fluids or even transfusion.

FAQs on What is Melena

Melena is a condition where stool appears jet-black, sticky, and foul-smelling due to digested blood from bleeding in the upper gastrointestinal tract.

Common causes include bleeding ulcers, gastritis, varices, tears or lesions in the oesophagus, and less commonly, gastric cancer or other digestive-tract disorders.

Consuming dark foods or taking iron supplements and bismuth-containing medications can temporarily darken stool, but this should not be confused with Melena.

Symptoms include black, tar-like stools with a foul odour, weakness, dizziness, rapid heartbeat, pale skin, and fatigue. Additional symptoms may include abdominal pain and vomiting blood.

Diagnosis involves a stool test and possibly an endoscopy to find and treat the cause. Treatment depends on the underlying issue, such as acid-blocking drugs for ulcers or banding for varices. Significant blood loss may require fluids or transfusion.