What should you know about constant diarrhoea after eating?

A meal can trigger loose stools when a person cannot digest a food component, such as lactose, or when a gut infection is present. Food poisoning and gastroenteritis may cause diarrhoea with cramps, nausea, vomiting, or fever. Coeliac disease, Crohn's disease, irritable bowel syndrome, giardiasis, and an overactive thyroid can also be considered when symptoms persist or recur.

Note the timing, portion, ingredients, pain, urgency, stool appearance, weight change, fever, and travel history. A food diary can reveal a pattern, but removing many foods without guidance can make nutrition harder and may obscure the diagnosis.

Drink regularly and replace lost salts with an oral rehydration solution when stools are frequent. Choose simple meals while symptoms are active and avoid foods that clearly worsen them. Wash hands carefully, especially after using the toilet and before preparing food. Arrange a medical review if the problem continues, returns often, or affects daily eating.

Get urgent help for blood or black stools, severe abdominal pain, fainting, confusion, repeated vomiting, marked weakness, or signs of dehydration. Prompt assessment is also needed for persistent fever, unexplained weight loss, or diarrhoea that wakes you from sleep.

Ask which tests may distinguish infection, intolerance, inflammation, or thyroid overactivity; whether any medicines could contribute; and how to maintain nutrition while the cause is investigated.