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What could it be?

What are the symptoms of gastroenteritis?

Gastroenteritis is a common condition that causes vomiting or diarrhoea. It's sometimes called 'stomach flu' or a 'vomiting bug'. Gastroenteritis means inflammation of the stomach and intestine and usually describes an infection of the gut.

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What are the symptoms of gastroenteritis?

The symptoms of gastroenteritis usually appear between half a day and three days after becoming infected. The main symptoms are:

In severe cases, people may have symptoms of dehydration.

If you think you or your child have gastroenteritis, find out what to do next by clicking here. This will tell you if you need to see a doctor and how to treat it.

In this series of articles centred around gastroenteritis you can read about the symptoms of gastroenteritis, the causes of gastroenteritis, and treatments for gastroenteritis -all written by one of our expert GPs.

The rest of this feature will take a in-depth look at the symptoms of gastroenteritis as, at Patient, we know our readers sometimes want to have a deep dive into certain topics.

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Key gastroenteritis symptoms

Diarrhoea and vomiting

Diarrhoea and vomiting are the main symptoms of gastroenteritis - some people have only one of these. Vomiting usually settles down within a few days, but diarrhoea can persist for longer. Diarrhoea means liquid, watery poo. People with watery diarrhoea often have to go to the toilet many times a day. The diarrhoea can contain mucus and sometimes blood. Diarrhoea and vomiting can lead to severe dehydration (see below).

Bloody diarrhoea

Bloody diarrhoea (dysentery) usually means you have a bacterial infection. People with bloody diarrhoea should contact a healthcare professional.


As with any other infection, some people get a fever. The fever is usually relatively mild in viral gastroenteritis (below 39°C) but can be higher in some other types.

Tummy pain

People with gastroenteritis may get tummy pain - usually felt as abdominal cramps or mild persistent discomfort. If you get more severe tummy pain then you should contact a doctor as it could be from other causes of abdominal pain, some of which can be serious.

Loss of appetite

People with gastroenteritis often lose their appetite and don't feel like eating. Always keep drinking fluids to avoid dehydration.

Weight loss

People with gastroenteritis sometimes lose weight during their illness, if they stop eating or eat less than usual.

Muscle aches

These may occur with viral infections that cause gastroenteritis.

Symptoms and signs of dehydration

Gastroenteritis may cause people to become dehydrated, particularly if they have stopped eating and drinking entirely, or are unable to keep anything down without vomiting. This can be very serious. Symptoms and signs of dehydration include:

  • Feeling light-headed or dizzy when standing up.

  • Having a dry mouth.

  • Feeling thirsty.

  • Not peeing as often as normal - for example, not peeing for 12 hours or in more severe cases not peeing for a whole day. Children who wear nappies may have fewer wet nappies.

  • Feeling drowsy - especially in children.

  • Looking pale.

  • Having skin that is slow to return to its usual shape when pinched - reduced skin turgor.

  • Having skin colour that is slow to return after being pressed - reduced capillary refill.

  • A fast heart rate.

People who think they may be dehydrated need to see a doctor immediately.

Continue reading below

Are gastroenteritis symptoms worse in some people?

Most people don't become seriously unwell with gastroenteritis, but some people are more likely to get worse symptoms - for example, if their immune system doesn't work as well, or because they find it more difficult to keep hydrated. These people include:

How serious is gastroenteritis?

The symptoms of gastroenteritis are unpleasant, but, in the UK and developed countries, it's rare for people to become seriously unwell. However, gastroenteritis is a common cause of childhood illness and deaths in other countries. It's estimated that globally, around 150,000 children under the age of five died from rotavirus infection - a type of viral gastroenteritis - in 2018.

The main risk of gastroenteritis is from dehydration. People who become severely dehydrated will require hospital treatment, and very severe dehydration can be fatal.

Sepsis due to gastroenteritis is rare, but can happen.

Some causes of gastroenteritis can cause other complications. For example, a rare strain of E. coli, called E. coli O157, can cause severe gut inflammation, kidney failure, and a life-threatening problem with blood clotting.

Continue reading below

Gastroenteritis symptoms in children

Gastroenteritis is a very common infection in children, and frequently caused by rotavirus infection. Rotavirus vaccination helps prevent children from becoming seriously ill with this infection.

There are several symptoms of gastroenteritis in children, including:

  • Diarrhoea.

  • Vomiting.

  • Reduced appetite.

  • A high temperature - fever.

  • Tummy pain.

  • Reduced activity levels - being less energetic than usual, or less playful.

Dehydration is the main risk in children and babies. Signs and symptoms of significant dehydration in children and babies include:

  • Not peeing as often - not peeing for 12 hours or more.

  • Becoming drowsy or more irritable.

  • Not being able to keep any fluids down without vomiting.

  • Not drinking anything, or breastfeeding at all.

  • In babies, having a sunken fontanelle - the soft spot on the top of the skull.

  • In serious cases, becoming floppy, inconsolable or very drowsy and difficult to wake.

Children with gastroenteritis can also have the following symptoms, but these can also be caused by more serious illnesses as well:

  • Continuous tummy pain that does not go away with paracetamol.

  • Bloody diarrhoea.

Children who are dehydrated, have continuous tummy pain or have bloody diarrhoea should be seen by a doctor immediately.

When to see a doctor for gastroenteritis symptoms?

Most cases of gastroenteritis get better without any treatment from a doctor and can be managed at home.

You should see a doctor if:

  • Symptoms of gastroenteritis are getting worse after the first two days.

  • Symptoms of gastroenteritis have not improved after seven days.

  • There is blood in the diarrhoea.

  • You have recently returned from an overseas trip to somewhere with poor sanitation.

  • You have a high fever.

  • You have severe tummy pain.

  • You, or your child, have any of the signs and symptoms of dehydration detailed above.

  • You have other serious medical problems, such as kidney disease or a severely weakened immune system.

  • You are otherwise worried that you, or your child, is getting worse or could be seriously unwell.

How is gastroenteritis diagnosed?

Gastroenteritis is usually diagnosed based on the presence of typical signs and symptoms, and often doesn't require any tests. Tests that might be done, in some cases, include:

  • Poo (stool) tests - usually done to look for specific causes of bacterial or parasitic gastroenteritis. Sometimes viruses are tested for too.

  • Blood tests, such as kidney function tests to look for signs of severe dehydration. These will usually only be done in hospital.

  • Ultrasound or CT scans of the tummy - these don't show any abnormalities in gastroenteritis, but might be done to look for other conditions. These would only be done in hospital.

What else could it be?

Other conditions - such as diarrhoea and vomiting - can sometimes cause similar symptoms to gastroenteritis. These should be considered if the symptoms are not typical for gastroenteritis - such as if there is severe abdominal pain - people are very unwell, or symptoms are not settling within the usual timeframe. It can also be difficult to tell gastroenteritis apart from other more serious conditions in some groups, such as older people and infants.

Examples include:

Further reading

Article history

The information on this page is peer reviewed by qualified clinicians.

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