Gastroenteritis in adults

Gastroenteritis in adults


Gastroenteritis is a common condition where the stomach and intestines become inflamed. It is usually caused by a viral or bacterial infection.

The two main symptoms of gastroenteritis are diarrhoea and vomiting.

Read more about the symptoms of gastroenteritis.

What causes gastroenteritis?

In the UK, the two most common causes of gastroenteritis in adults are the norovirus and food poisoning (most often caused by salmonella or campylobacter bacteria).

These infections can interfere with the absorption of water and salts from the contents of your intestines into the body, which is why the most common symptom of gastroenteritis is watery diarrhoea and why there is a risk of dehydration.

Gastroenteritis can also have a number of other causes, including a rotavirus infection, although this is more common in children. Read more about gastroenteritis in children.

Seeing your GP

There’s usually no need to see your GP if you have gastroenteritis because the symptoms are normally shortlived.

If your symptoms are severe or last longer than a few days, your GP may ask for a stool sample so that it can be checked for a specific bacterium or parasite. If a bacterium or parasite is identified, appropriate medication can be prescribed to treat the infection.

In some cases, blood tests and urine tests may be used to rule out other conditions.

Treating gastroenteritis

Most people don’t need any specific treatment for gastroenteritis, but it’s important to make sure you drink plenty of fluids to reduce your risk of dehydration.

An oral rehydration solution can be used by people who are particularly vulnerable to the effects of dehydration, such as elderly people or those with another existing condition.

Medications to treat the symptoms of gastroenteritis are not usually necessary, but they may be recommended if your diarrhoea or vomiting is particularly severe.

If there is a risk of you becoming significantly dehydrated, you may need to be admitted to hospital for treatment. This is because severe dehydration can be very serious and even potentially fatal in rare cases.

Read more about treating gastroenteritis.

Preventing gastroenteritis

As gastroenteritis is highly infectious, it is important to take steps to prevent it spreading to other people. These include:

  • washing your hands thoroughly with soap and water or an antibacterial hand wash after going to the toilet and before eating or preparing food
  • cleaning the toilet, including the handle and the seat, with disinfectant after each bout of vomiting or diarrhoea
  • not sharing towels, flannels, cutlery or utensils with other members of your household
  • not returning to work until you have had no symptoms for at least 48 hours

If you are frail, or have an underlying condition affecting your intestines or immune system, it may be useful to seek advice from your GP or a specialist before travelling to an area where there is a risk of picking up a gastrointestinal infection.

Read more about preventing gastroenteritis.

Symptoms of gastroenteritis in adults

Depending on the specific cause, the symptoms of gastroenteritis can take anything between a few hours and a few days to develop after you are infected.

The main symptom is repeated diarrhoea, which may sometimes contain traces of blood or mucus.

Other symptoms can include:

  • vomiting
  • feeling sick
  • loss of appetite
  • stomach cramps
  • aching limbs
  • headaches
  • a high temperature (fever)

Signs of dehydration

Gastroenteritis can cause dehydration, which can be more serious than the infection itself. Elderly people are particularly at risk from the effects of dehydration, which, if not treated, can be fatal.

You should therefore be aware of symptoms that may suggest you or someone in your care is becoming dehydrated.

Signs of mild dehydration can include:

Signs of more severe dehydration can include:

  • weakness and apathy (a lack of emotion or enthusiasm)
  • muscle cramps
  • pinched face
  • sunken eyes
  • passing little or no urine
  • confusion
  • rapid heartbeat

When to seek medical advice

In most cases, there’s no need to see your doctor if you have gastroenteritis because the symptoms usually pass in a few days without any specific treatment.

However, you should contact your GP if:

  • your symptoms do not begin to improve after a few days
  • repeated episodes of vomiting mean that you are unable to keep down any fluids
  • there is blood or mucus in your stools
  • you have signs of more severe dehydration (see above)
  • you think you may have been infected while travelling in a part of the world with a poor standard of water hygiene in the previous few weeks
  • you are over 65 years of age
  • you are pregnant
  • you have a bowel disease, such as Crohn’s disease or ulcerative colitis
  • you have a weakened immune system caused by another condition, such as HIV, or as the result of medical treatment, such as chemotherapy

If your GP is unavailable, contact your local out-of-hours service or call NHS 111 for advice.

Causes of gastroenteritis in adults

Gastroenteritis is usually caused by an infection of the stomach and intestines.

The infection interferes with the absorption of water from the contents of your intestines into the body, which is why watery diarrhoea is the most common symptom of gastroenteritis and why dehydration can occur.

In the UK, the two most common causes of gastroenteritis in adults are a norovirus infection and bacterial food poisoning.


Norovirus is the most common cause of viral gastroenteritis in adults. It is sometimes referred to as the “winter vomiting bug” because it tends to be more widespread during the winter months. However, infections can occur at any time of the year.

The virus is passed out in the stools (faeces) of someone with the infection and, if the person does not wash their hands after going to the toilet, the virus can be transferred to any surfaces, objects and food they touch, where it can survive for several days.

The infection can then be passed to someone else who eats contaminated food or touches a contaminated object or surface and then touches their mouth.

Small droplets of infected faeces or vomit can also be carried in the air, which others can breathe in.

Norovirus infections are easily spread in these ways, particularly in confined environments, such as hospitals, nursing homes, schools and cruise ships.

There are many different types of norovirus and it is possible for you to get a norovirus infection several times. This is because any immunity to the infection you develop after being ill only lasts a few months.

Read more about norovirus infections.

Food poisoning

Most bacterial infections that cause gastroenteritis are the result of food poisoning.

Contamination with bacteria can occur at any stage during the food’s production, processing or cooking. For example, food poisoning can be caused by:

  • not cooking food at the right temperature or for the right length of time
  • not chilling food at the correct temperature
  • someone who has not washed their hands properly handling the food 
  • eating food after it has reached its use-by date
  • cross-contamination (when harmful bacteria is spread between food, surfaces and equipment)

The most common types of bacteria that are associated with gastroenteritis are called campylobacter, salmonella and escherichia coli (E. coli). These are generally found in raw or undercooked meat, unpasteurised milk and untreated water.

Read more about food poisoning.

Travel infections

Travellers to areas with poor levels of sanitation and water hygiene are also at risk of developing gastroenteritis. This is often known as “traveller’s diarrhoea”.

Traveller’s diarrhoea can be caused by a range of bacteria, viruses or parasites, often similar to those infections acquired through food poisoning in the UK. Other causes include:

  • the shigella bacterium or the entamoeba parasite – these are both spread through poor hygiene and cause a type of traveller’s diarrhoea called dysentery
  • cryptosporidium – a parasite found in soil, food and water that has been contaminated with animal or human faeces
  • giardia intestinalis – a parasite found in water that has been contaminated with animal or human faeces (infections that are caused by this parasite are known as giardiasis)

Read more about preventing traveller’s diarrhoea.

Treating gastroenteritis in adults

Most cases of gastroenteritis do not require treatment and the symptoms will improve in a few days, although medication may be recommended if the condition is severe.

Looking after yourself

It’s important to drink plenty of fluids to avoid dehydration, so you should try to make sure you have small and frequent sips of water. Fruit juice and soup can also help avoid dehydration in adults with gastroenteritis.

If you are more vulnerable to the effects of dehydration – for example, if you are elderly or have an underlying health condition – oral rehydration solutions may be recommended in addition to drinking plenty of fluids.

These solutions usually come in sachets and are available without a prescription from your local pharmacist. You dissolve them in water to make a drink that helps replace salt, glucose and other important minerals that your body loses if you are dehydrated.

If you think you may be at risk of dehydration, speak to your GP or pharmacist about whether oral rehydration solutions are suitable for you.

If you feel like eating, try to maintain a normal, healthy diet. You will be able to tolerate light, plain foods, such as rice or wholemeal bread, better than fatty, sugary, spicy or rich foods. It may be better to eat six light meals a day rather than three large meals.

You should stay away from work until you have had no symptoms for at least 48 hours to reduce the risk of spreading the infection to others.


If your symptoms are particularly severe, your GP may recommend some of the medications described below.

Antidiarrhoeal medications

Antidiarrhoeal medications are sometimes used to reduce diarrhoea. 

Loperamide is a widely used antidiarrhoeal medication for treating gastroenteritis. It slows down the movement of your bowel contents and also increases water absorption from the gut.

Constipation and dizziness are two common side effects of loperamide. Rarer side effects include stomach cramps, drowsiness, rashes and bloating.

Loperamide is not suitable for people with ulcerative colitis or dysentery (where you have diarrhoea containing blood or mucus and a fever) and shouldn’t be used if you are pregnant. However, it can be used safely while breastfeeding.

Antidiarrhoeal medication should not be used by children under the age of 12 unless directly instructed by your GP.

Anti-emetic medications 

Anti-emetic medications, such as metoclopramide, are sometimes used to help prevent or reduce vomiting.

Metoclopramide can be given as tablets or an injection. It helps relax the muscles used during vomiting while also speeding up the absorption of fluids and foods by the digestive system.


Antibiotics are not usually recommended for treating gastroenteritis because many cases are caused by viruses rather than bacteria. Even when bacteria is responsible, antibiotics have often been found to be no more effective than simply waiting for the symptoms to pass.

However, antibiotics may be recommended if you have particularly severe gastroenteritis and a specific bacterium has been identified in a stool sample.

Side effects of using antibiotics to treat gastroenteritis include a metallic taste in your mouth, feeling sick and vomiting.

Hospital treatment

Hospital treatment may be required for people with serious dehydration caused by gastroenteritis.

For example, admission to hospital may be recommended if:

  • repeated episodes of vomiting mean that you are unable to keep down any fluids
  • you have symptoms that suggest severe dehydration, such as not passing any urine
  • you have an underlying medical condition, such as Crohn’s disease or HIV, that means you are at an increased risk of developing serious problems

Treatment in hospital will involve administering fluids and nutrients directly into a vein (intravenously).

Preventing gastroenteritis in adults

As gastroenteritis is very infectious, it is important to take steps to prevent it spreading to other people.

To prevent the spread of infection:

  • wash your hands thoroughly after going to the toilet and before eating or preparing food
  • clean the toilet, including the seat and handle, with disinfectant after each episode of vomiting or diarrhoea
  • don’t share towels, flannels, cutlery and utensils with other household members
  • don’t return to work until you have had no symptoms for at least 48 hours

Read more about how to prevent germs spreading.

Food hygiene

Practising good food hygiene will help you avoid getting gastroenteritis from food poisoning. You should:

  • regularly wash your hands, surfaces and utensils with hot, soapy water
  • never store raw and cooked foods together
  • make sure that food is properly refrigerated
  • always cook your food thoroughly
  • never eat food that is past its use-by date

Read more about preventing food poisoning.

Preventing traveller’s diarrhoea

If you are travelling in a country with poor levels of food and water hygiene, you can reduce your risk of picking up an infection by avoiding:

  • tap water
  • raw or undercooked meat
  • ice cream or ice cubes
  • shellfish
  • eggs
  • salads
  • fruit and vegetables that have been peeled or have damaged skin
  • unpasteurised milk, cheese and other dairy products

Food and drink that is usually safe includes:

  • sealed bottled water
  • water that has been boiled for at least one minute (including tea or coffee)
  • food that has been thoroughly cooked and remains steaming hot prior to serving
  • canned food or food in sealed packs
  • fresh bread
  • fruit that you wash (with bottled or boiled water) and peel yourself
  • alcohol

Before travelling, you should also ensure you have all the necessary travel vaccinations for the area you are visiting.

Read more about preventing traveller’s diarrhoea and food and water abroad.