Most sudden diarrhoea is caused by an infection and settles within a few days without specific treatment. The most important step is to replace lost fluid. Antibiotics are rarely needed. Some symptoms, and some people, need prompt medical assessment.

What is it?

Acute diarrhoea means three or more loose or watery stools a day for less than two weeks. It is usually caused by gastroenteritis, an infection with a virus (such as norovirus) or, less often, bacteria or parasites, sometimes with vomiting, cramps and mild fever. Food poisoning, some medicines (including antibiotics) and a flare of an existing bowel condition can cause similar symptoms.

This leaflet is mainly for adults. Babies and young children can become dehydrated quickly; the warning signs in children are listed below, and a child with any of them should be seen by a doctor the same day.

Replace fluids first

• Drink small amounts often, even if you are vomiting
• Oral rehydration solution (ORS), available from pharmacies as sachets, replaces water and salts in the right balance. It is especially useful for older people, those with other health conditions, and anyone with heavy diarrhoea
• In mild cases, water, soups, laban and weak tea also help
• Avoid undiluted fruit juice, fizzy drinks and energy drinks; their high sugar content can make diarrhoea worse
• Aim to pass pale yellow urine regularly. You will need more fluid in hot weather

Eating

Eat normally as soon as you feel able; there is no need to stop food, and eating helps the bowel recover. Simple foods such as rice, bread, potatoes, bananas, soups, yoghurt and laban are good choices; avoid very fatty or fried meals for a day or two if they upset you. If plain milk worsens diarrhoea, reduce it for a short time.

Medicines

• Antibiotics are not needed in most cases; even bacterial diarrhoea usually settles without them, and unnecessary antibiotics raise the risk of C. difficile infection. Your doctor may prescribe one for severe illness, bloody diarrhoea with fever, some travellers, or weakened immunity. Do not take leftover antibiotics or buy them without a prescription
• Loperamide can reduce stool frequency in adults for a day or two. Do not take it if you have blood in the stool, a high temperature or severe abdominal pain, and do not give it to children unless a doctor advises. Do not take more than the dose on the pack, stop if you are not better within 48 hours, and do not use it after recent antibiotics unless a doctor advises
• Paracetamol can be used for fever or aches
• Probiotics: evidence in adults is mixed, and they are not needed
• If you take medicines for diabetes, blood pressure (especially water tablets), or heart or kidney conditions, ask your doctor or pharmacist whether any should be paused while you are dehydrated or unable to drink well. Do not stop any medicine, especially insulin, without this advice; check your blood sugar more often and seek advice if it is high or low. Avoid anti-inflammatory painkillers such as ibuprofen while dehydrated
• Diarrhoea and vomiting can reduce the effect of the contraceptive pill; check the leaflet or ask a pharmacist

Preventing spread and future episodes

• Wash your hands with soap and water after using the toilet and before preparing food. Alcohol gel is less effective against some viruses, such as norovirus
• Do not prepare food for others while unwell, and stay off work or school until 48 hours after the last episode of diarrhoea or vomiting
• Clean toilets, taps and door handles with a bleach-based cleaner
• Refrigerate cooked food, especially rice, meat and dishes with mayonnaise, within an hour or two, and reheat until piping hot
• Take extra care with food at buffets, large gatherings and roadside stalls on hot days

Travellers

When travelling to places where water and food hygiene may be less reliable:

• Drink sealed bottled water, and avoid ice unless it is made from safe water
• Choose freshly cooked hot food, peel fruit yourself, and avoid raw salads and unpasteurised milk
• Carry oral rehydration sachets
• Seek medical advice if you develop fever or bloody diarrhoea, or if symptoms continue after you return home

Common questions

This leaflet is general information and does not replace advice from your own doctor. Version 1.0, October 2026. Next review October 2028.