Acute bloody diarrhoea may be commonly encountered in the acute medical unit. Among young patients, the main differential diagnoses are acute infectious colitis, and first presentation of inflammatory bowel disease (IBD). A combination of clinical, laboratory, radiological, endoscopic and histological investigations are required to make the diagnosis. If inflammatory bowel disease is suspected, then the patient should be admitted to a specialist gastroenterology ward and receive input from the surgical team, IBD nurses and specialist stoma nurses. Intravenous steroid therapy for acute severe disease should be started before stool cultures are back unless there is a strong clinical suspicion of amoebiasis. All patients require thromboprophylaxis and close attention paid to fluid balance and nutritional requirements. Daily clinical review is required. The Travis criteria may be employed at day 3 to assess the likelihood of requiring surgery and plans for rescue therapy, medical or surgical should be made between day 3-7 if the patient is not responding adequately to initial medical therapy.