The real reason your stool turned black overnight: The warning signs of Melena you should never ignore |

Finding your stool suddenly dark black and tar like can be deeply unsettling. Many people immediately assume it is caused by something they ate, but a drastic colour change, especially when the stool looks sticky or has a strong unpleasant smell, can indicate something far more serious. Stools reflect what happens inside the digestive system, so sudden black colour may point towards internal bleeding, infection or complications linked to the stomach or upper intestine. Although sometimes the reason is harmless, the possibility of a medical emergency makes it important not to dismiss the symptom. Knowing how to recognise the difference between harmless discolouration and dangerous internal causes can help protect your health and prevent complications.A peer-reviewed clinical study published in 2021 in Frontiers found that most cases of black tar-like stool, medically known as melena, are linked to upper gastrointestinal bleeding involving the stomach, oesophagus or upper small intestine. The study noted that ulcers and inflammatory conditions were the most frequent causes of bleeding that led to melena.

What does black stool mean in medical terms

Black stool with a tar-like texture typically means that blood has travelled through the digestive tract and become digested. As it mixes with stomach acids and bacteria, it turns dark and sticky. This is different from harmless black stools caused by medicines or foods.Melena often indicates bleeding from ulcers, inflammation, ruptured blood vessels or damage to the protective lining of the stomach or small intestine. Doctors regard this as a warning symptom that should be evaluated quickly, especially when accompanied by weakness or dizziness.

Common causes of black stool that require medical attention

Bleeding stomach ulcers

Ulcers caused by infection, excessive acid, stress or painkiller overuse can bleed slowly, leading to black stools over several days.

Gastrointestinal bleeding

Bleeding in the oesophagus, stomach or duodenum may occur due to inflammation, varices or tears caused by severe vomiting.

Gastritis

Inflammation of the stomach lining can lead to bleeding, pain and vomiting. Alcohol, spicy food, stress and medication can worsen it.

Cancer or polyps

Though less common, growths inside the digestive system can bleed and change stool colour.

When black stool may be harmless

In some cases, black stool can result from:

These causes usually produce dark stool without a tar-like texture or foul smell. The colour often returns to normal within a day or two after stopping the food or supplement.

Warning signs you should never ignore

Black tar-like stool combined with any of the following requires urgent medical help:

These signs may point to active bleeding or severe infection that needs emergency care.

How doctors diagnose the cause of black stool

Doctors may perform:

Treatment can include antibiotics, acid-reducing medicines, medication to stop bleeding or endoscopic interventions.

What to do if you notice black tar-like stool

Acting early can prevent severe complications.Black stool is not always dangerous, but when it appears tar-like, sticky or foul-smelling, it often signals internal bleeding rather than simple food effects. The body rarely sends strong warning signs without reason, and stool colour is one of its clearest messages. Paying attention, responding quickly and getting medical evaluation can protect your long-term health.Disclaimer: This content is intended purely for informational use and is not a substitute for professional medical, nutritional or scientific advice. Always seek support from certified professionals for personalised recommendations.Also read| Can heaters make asthma WORSE? The truth that respiratory experts want you to know