Bloody diarrhoea: what to know

Blood may be bright red, dark, mixed through the stool or visible on tissue, and these patterns can have different explanations. Food Poisoning and Gastroenteritis can inflame the bowel. Crohn's Disease may cause recurring diarrhoea with pain, weight change or fatigue. Coeliac Disease, Food Intolerance, Giardiasis and Hyperthyroidism can alter bowel function, although blood is not a defining feature of every one of them. Irritable Bowel Syndrome does not explain visible blood, so bleeding should be assessed separately. A diarrhoea symptom does not reveal which condition is present.

Record when the bleeding started, how often stools occur, whether blood is mixed in, and any pain, fever, weight change or recent travel. Drink regularly and choose simple foods if tolerated. Avoid medicines that stop bowel movement until a clinician has advised you, particularly if you have blood or fever. Arrange medical review if the symptom is new, recurring or unexplained.

Seek urgent help for heavy or repeated bleeding, black stools, severe pain, faintness, confusion, persistent vomiting, a high fever or signs of dehydration such as very little urine. Sudden worsening, or bloody diarrhoea in a child, frail adult or person with immune problems, warrants prompt assessment.

Ask what examinations or stool tests may clarify the cause, whether medicines could be contributing, and how to maintain hydration while waiting for results. Bring a list of medicines and recent food, travel or infection exposures.