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Health education · DigestionDigestive health

Gastroenteritis and dehydration: symptoms, care and when to seek help

Gastroenteritis, often called “stomach flu,” mainly causes diarrhea, stomach cramps, nausea and vomiting.1

Most people recover at home without medication.1 The priority is to stay hydrated and watch the person’s general condition, especially in young children and more vulnerable people.

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Causes

What are the causes?

Gastroenteritis can be caused by a virus, bacteria or a parasite. Norovirus is the most common cause in adults, and rotavirus in children. These viruses mostly circulate in fall and winter.1

Gastroenteritis is very contagious.1

It can spread through:1

  • direct contact with a sick person;
  • contaminated hands, objects or surfaces;
  • contaminated water or food;
  • droplets released during vomiting.

Symptoms

What are the symptoms?

Symptoms usually last 24 to 72 hours, and up to 10 days when the illness started during or after a trip abroad.1

Symptoms that get worse or persist call for a reassessment.

Possible signs:1

  • diarrhea;
  • stomach cramps;
  • nausea and vomiting;
  • sometimes a mild fever, headache, muscle aches, loss of appetite or a change in general condition.

Dehydration

How do you recognize dehydration?

Diarrhea and vomiting cause a loss of water and minerals. If these losses are not replaced, dehydration can occur.

In adults3

  • a dry mouth;
  • intense thirst;
  • little urine, dark in colour;
  • weakness.

In children2

  • mild dehydration: drier mouth and tongue, more thirst, fewer wet diapers;
  • moderate to severe dehydration: no tears when crying, drowsiness or irritability, sunken eyes, fewer than 4 wet diapers in 24 hours.

Don’t wait for every sign to appear before asking for advice. In a child, moderate to severe dehydration means seeing a doctor promptly or going to the emergency room.2

People at risk

Who should be watched more closely?

The risk of complications is higher in:1,4

  • children under 2;
  • people aged 65 and older;
  • pregnant people;
  • people with a weakened immune system;
  • people with a chronic disease, such as diabetes.

For a child under 2, call Info-Santé at 811, option 1, whatever the symptoms.1

Rehydration

How should you rehydrate?

Rehydration and good nutrition are the two main treatments.1 Drink often, in small amounts.3

An oral rehydration solution, sold in pharmacies, replaces lost water and minerals. It comes as a ready-to-serve liquid, powder sachets or frozen pops. The Canadian Paediatric Society recommends ready-to-serve products and suggests keeping some at home.2 Ask your pharmacist to help you choose the right product, especially if you have diabetes or need to limit fluids.

For babies and young children

To prevent dehydration: continue the usual milk and offer drinks more often; use a cup, spoon, dropper or straw if needed.2 Continue breastfeeding or formula, in smaller amounts more often.3

If your child has a lot of diarrhea or vomiting and refuses to drink, offer small amounts of oral rehydration solution, for example 5 to 15 ml every 5 to 15 minutes.2

With mild dehydration: a breastfed baby nurses more often for shorter times, with rehydration solution between feeds, even if vomiting. For a formula-fed baby, formula is stopped for about 4 hours while the solution is given, then resumed after 3 to 4 hours.2

Juice, soft drinks (even flat), sports drinks, rice water and plain water don’t contain the right amounts of sugar and salt to rehydrate a child.2

Eating

What should you eat during gastroenteritis?

Eat small meals and increase portions gradually, as tolerated.3

Choose light foods:3

  • rice, white pasta or bread;
  • eggs;
  • lean meats;
  • unsweetened cereals.

For now, avoid soft drinks, fruit juice, tea, coffee and energy drinks.3 For a child who eats solid food and is vomiting, food can be paused for about 4 hours while giving rehydration solution by spoon, then usual foods are gradually reintroduced; most children eat normally again within 1 to 2 days.2

Medications

Should you take medication?

Most people recover without medication: rehydration remains the main treatment.1

For pain, acetaminophen or ibuprofen can be used; ibuprofen is contraindicated under 6 months.3 In children, it is also not suitable in case of dehydration.5

Ask your pharmacist before taking or giving a medication for diarrhea or vomiting, for adults and children alike.3

Seeking care

When should you see a professional?

These timelines are not a reason to wait if you have trouble drinking or signs of dehydration. If in doubt, call Info-Santé at 811, option 1, any time.3

According to Santé Québec, see a professional in particular if:3

  • vomiting or diarrhea lasts more than 2 days despite following the advice;
  • diarrhea lasts more than 7 days;
  • fever lasts more than 2 days despite medication;
  • diarrhea started during or after a trip abroad;
  • you can no longer take your usual medications;
  • your immune system is weakened and you have had diarrhea for 24 hours;
  • you take blood thinners and have had diarrhea or vomiting, or have been unable to eat, for 24 hours;
  • a baby under 2 months has diarrhea: see a professional within 24 hours;
  • a child has had mucus in the stool for more than 2 days.

When should you go to the emergency room?

Go to the hospital without waiting if there is:1,3

  • significant drowsiness, difficulty staying awake, confusion or agitation;
  • signs of dehydration despite drinking enough;
  • no urine for more than 12 hours with intense thirst;
  • vomiting that continues after 4 to 6 hours;
  • severe abdominal pain with a hard belly;
  • blood in vomit, a lot of blood in the stool or black stools;
  • fever in someone who is immunocompromised, pregnant, or a baby under 3 months;
  • in a child: signs of dehydration, such as fewer tears when crying, or a baby who cries intensely and cannot be comforted;
  • in a child: refusing to drink for 4 to 6 hours or more, or green vomit.1

Call 911 if the situation is serious and urgent.5

Prevention

How can you avoid spreading gastroenteritis?

  • wash your hands often with soap and water, especially after using the toilet or changing a diaper and before eating or preparing food;1,4
  • clean and disinfect contaminated and frequently touched surfaces;3,4
  • wash soiled clothing and linens right away;4
  • don’t prepare or serve food for others while you are sick;3,4
  • have babies vaccinated against rotavirus, according to the schedule.1

People are most contagious while they have symptoms, but they can remain contagious afterward. For norovirus, this lasts at least 3 days after recovery, and sometimes up to 3 weeks.4 Keep up strict hygiene during recovery.

SettingTime after diarrhea and vomiting stop
Child care24 hours3
School, work and group activities48 hours3
People who handle food at work48 hours1

Also follow any specific instructions from your setting, especially during an outbreak.

When to consult at the Clinique IPS du Palais?

Depending on the symptoms and availability, various common health problems can be assessed at the clinic, in adults and children. A nurse practitioner can assess hydration, check for warning signs and tailor the advice.

If there are signs of moderate to severe dehydration, blood in the stool or vomit, or a worsening general condition, go to the emergency room without waiting.

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Sources

  1. Government of Québec. Gastro-entérite (in French). Updated July 27, 2026, accessed October 29, 2026. quebec.ca
  2. Institut national de santé publique du Québec (INSPQ). Déshydratation, Mieux vivre avec notre enfant de la grossesse à deux ans (in French). Updated February 17, 2026, accessed October 29, 2026. inspq.qc.ca
  3. Santé Québec. Gastroentérite (health advice, in French). Updated January 1, 2026, accessed October 29, 2026. sante.quebec
  4. Public Health Agency of Canada. Preventing norovirus infections. December 2, 2022, accessed October 29, 2026. canada.ca
  5. Institut national de santé publique du Québec (INSPQ). Fièvre, Mieux vivre avec notre enfant de la grossesse à deux ans (in French). Updated February 17, 2026, accessed October 29, 2026. inspq.qc.ca

This sheet provides general information and does not replace an assessment by a health professional. Published October 29, 2026.