What should you know about diarrhoea and fever?

Diarrhoea means passing loose or watery stools more often than is normal for you. Fever is a rise in body temperature that can occur when the immune system responds to infection. Together, they commonly occur with gastroenteritis, food poisoning, or another infection affecting the digestive system.

The pattern matters. Cramping, nausea, vomiting, tiredness, and reduced appetite may accompany an upset gut. Ongoing or repeated diarrhoea can also have non-infectious causes, including food intolerance, coeliac disease, inflammatory bowel conditions such as Crohn's disease, irritable bowel syndrome, or an overactive thyroid. These conditions are not diagnosed from fever and diarrhoea alone.

Take frequent small sips of water or an oral rehydration drink. If you are vomiting, small amounts spaced closely may be easier to keep down. Continue eating if you feel able; choose simple foods and avoid alcohol. Wash your hands carefully after using the toilet and before preparing food, and avoid preparing meals for other people while you are unwell.

Keep track of how often you pass stool, whether you can drink, and whether you are passing urine. Rest, and check your temperature with a thermometer if possible. Ask a pharmacist or clinician before taking an anti-diarrhoeal medicine, especially if you have a high fever, blood in the stool, severe abdominal pain, or a significant medical condition.

Arrange prompt medical assessment if you cannot keep fluids down, have signs of dehydration such as very little urine, marked dizziness, unusual sleepiness, or a dry mouth, or the diarrhoea is severe or not settling. Contact a clinician urgently for blood or black stool, severe or worsening abdominal pain, confusion, breathing difficulty, or a fever with a rapidly deteriorating condition.

Babies, older adults, pregnant people, and people with weakened immunity or significant long-term illness can become dehydrated more quickly. They should seek advice early. A recent trip, antibiotic course, hospital stay, or contact with someone who has similar symptoms is useful information for the clinician.

You could ask: What is the most likely cause of these symptoms? Do I need testing or treatment? Which fluids and foods are suitable for me? Which medicines should I avoid? What signs mean I should return or seek urgent help?