Gastroenteritis is an infection of your stomach and bowel (gut) causing vomiting, nausea, diarrhoea and abdominal pain. It’s sometimes called a stomach bug.

By Wallace Health I Medically reviewed by Adrian Roberts.
Page last reviewed: October 2018 I Next review due: October 2023

What is gastroenteritis?

Around one in five adults gets gastroenteritis each year. Many germs (bacteria, viruses or other parasites) can cause gastroenteritis, though it’s most often due to a virus or bacterial food poisoning.

Viral gastroenteritis, also known as a stomach flu or a stomach virus, is commonly due to viruses called norovirus, rotavirus or adenovirus.

Common examples of bacteria that can infect food include:

  • Salmonella
  • Campylobacter
  • Shigella
  • Escherichia coli (E. coli)

How to tell if you have gastroenteritis

Gastroenteritis symptoms include:

Vomiting usually lasts for the first day or so. Diarrhoea can last for up to a week before getting back to normal.

Talk to your doctor if you’re concerned about symptoms

You can book an appointment with a Spire private GP today.

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Diagnosis and tests for gastroenteritis

Usually, gastroenteritis symptoms are quite mild and can be managed at home. However, you should see a GP if you have diarrhoea for more than seven days or are vomiting for more than two.

You should also seek medical advice if:

  • You’re pregnant or your baby or child has gastroenteritis symptoms
  • You’re elderly or immunocompromised (have a weakened immune system) – for example, if you’re receiving chemotherapy or have HIV
  • You have an underlying condition such as diabetes, epilepsy, inflammatory bowel disease or kidney disease
  • You keep vomiting and are unable to drink or you’re dehydrated despite using oral rehydration sachets
  • You have blood in your stools or vomit, or vomit that’s green or yellow
  • You have severe abdominal pain

If you need to see a GP, they’ll ask you about:

  • Recent travel
  • Whether you’ve been in contact with anyone else with similar symptoms
  • If you’ve recently taken antibiotics or been in hospital

They may check you for signs of dehydration, take your temperature, pulse and blood pressure, and examine your abdomen.

If you have severe gastroenteritis, you’ve travelled abroad or you have blood in your stool or vomit, a stool sample will be taken and analysed to look for the specific cause.

Causes of gastroenteritis

Viruses are spread easily between people by:

  • An infected person not washing their hands after going to the toilet
  • Touching surfaces or objects an infected person has touched
  • Eating food prepared by an infected person

Food poisoning can be due to:

  • Poorly cooked or reheated food (in particular shellfish or chicken)
  • Food that’s been left at room temperature for too long or not stored (refrigerated or frozen) correctly
  • Food being handled by someone who’s ill or hasn’t washed their hands
  • Eating food after its use-by date

In countries with poor sanitation, water may also be infected with bacteria or other germs.

Common treatments for gastroenteritis

Most of the time, gastroenteritis can be managed at home by:

  • Drinking lots of fluid – ideally water or rehydration sachets
  • Eating as normally as you can but in smaller portions and avoid fatty, spicy or heavy foods
  • Taking anti-diarrhoeal medication – though they may not be suitable for everybody so always check the label
  • Painkillers such as paracetamol or ibuprofen can help reduce a high temperature (fever) and provide headache relief

Although symptoms may be unpleasant, you should be back to normal within a few days.

If your symptoms are severe and you need to see your GP, they may recommend a course of antibiotics if a stool sample analysis has confirmed a bacterial infection.

If you become severely dehydrated, you may need to be admitted to hospital so you can be given fluids through an intravenous (IV) saline solution or a tube through the nose.