What should you know about dark loose stool causes?

Foods with deep pigments can temporarily darken stool. Iron supplements and some medicines can also change its colour. Loose stool at the same time may reflect a stomach bug, food poisoning, a food intolerance, or another digestive condition. Gastroenteritis often brings diarrhoea with cramps, nausea, or vomiting; Giardia can cause persistent, unpleasant-smelling diarrhoea after contaminated food or water. Coeliac disease, Crohn's disease, irritable bowel syndrome, and an overactive thyroid can also be associated with altered bowel habits, although dark stool alone does not identify any one condition.

Black, sticky, tar-like stool or dark stool mixed with blood needs prompt medical assessment because bleeding higher in the digestive tract is one possible explanation. A clinician will consider what you ate, medicines and supplements, how long the change has lasted, and whether you have pain, fever, weakness, or dizziness.

Think back over recent meals, iron products, and new medicines, and note the stool colour, texture, frequency, and any accompanying symptoms. Drink frequent small amounts of fluid; an oral rehydration drink may help if diarrhoea is ongoing. Choose simple foods as tolerated and avoid alcohol until you feel better. Do not stop prescribed medicine without advice. If the stool becomes black and tar-like, do not rely on home observation; contact a healthcare professional promptly.

Seek urgent help for black tarry stool, visible blood, faintness, confusion, severe or worsening abdominal pain, repeated vomiting, or signs of dehydration such as very little urine and marked dizziness. Arrange medical review if diarrhoea continues, keeps returning, follows recent travel, or is accompanied by fever, weight loss, or night-time symptoms. Children, older adults, pregnant people, and anyone with a long-term illness may need advice sooner.

Could a food, iron supplement, or medicine explain the colour? Does the stool look like bleeding rather than food pigment? Do I need a stool test or blood test? Which fluids and foods are suitable while the diarrhoea settles?