Signs and Symptoms of Stomach Flu

Medically known as viral gastroenteritis, the so-called stomach flu can cause nausea, vomiting, diarrhea, and other unpleasant symptoms.

Stomach flu, or viral gastroenteritis, is a condition where your stomach lining is inflamed. However, stomach flu symptoms are not similar to those of the actual flu. Symptoms like nausea, vomiting, and diarrhea are more likely the result of a gastrointestinal virus. True influenza only affects your airways.

Anyone can experience symptoms of the flu. Symptoms of the stomach flu usually show up one to three days after you're infected. Some cases are mild, lasting 24 or 48 hours. Cases usually last less than a week.

Watery Diarrhea

Watery diarrhea refers to really loose and watery bowel movements. This type of diarrhea happens because the infection prevents your large intestine from retaining fluid. Instead, it leaves your body in the form of loose, watery stools. Blood or mucus in your stool rarely occurs with the stomach flu; they are signs you should head to the emergency room.

Nausea and Vomiting

Nausea and vomiting are common symptoms of gastroenteritis. While certainly unpleasant, these symptoms are actually a good sign: Your body is trying to get rid of the bad stuff. Nausea helps protect you from ingesting toxic substances further, while vomiting is a way of removing them from your body.

Abdominal Pain

Abdominal cramps or abdominal pain are also common. This is the discomfort felt in between a person's chest and grown. The cramps or pain may feel like generalized pain—which spans over half of a person's belly—typical for stomach viruses.

Low-Grade Fever

Fevers refer to short-term body temperature increases due to diseases or illnesses. Low-grade fevers can be a stomach flu symptom—about 50% of individuals will have a fever. This is usually nothing to worry about, but a higher one might be. A temperature above 102°F may be a sign that dehydration is becoming severe.


Dehydration happens when a person doesn't get enough fluid to replace any lost. This condition is a complication of the stomach flu. It's a symptom that needs to be addressed since it can cause your condition to get even worse. If you're dehydrated, you may:

  • Feel dizzy, lightheaded, or confused
  • Feel tired
  • Feel very thirsty
  • Have a dry mouth
  • Less bounce of the skin when pressed
  • Sunken eyes or cheeks
  • Urinate infrequently and notice dark, yellow urine

Beyond the above symptoms, other specific dehydration signs in younger children include no wet diapers for three or more hours and tear-free crying.

Symptoms in Children

Gastroenteritis happens most often in children younger than 5 years old. Many stomach flu symptoms for infants and children are the same as those for adults. Children may also experience a low appetite, and mild vomiting may follow the onset of diarrhea.

When To See a Healthcare Provider

Though gastrointestinal viruses usually resolve with good self-care, there are some signs that you need urgent medical care. Go to an emergency room if you have any of these symptoms:

  • Black or tarry stools or stools containing blood or pus
  • Dehydration
  • Diarrhea for more than one day
  • Any fever in infants or high fever in older children and adults
  • Frequent loose stools
  • Frequent vomiting
  • Mental state changes
  • Severe abdomen or rectum pain

Infants and children will also need immediate medical care if they have any of the above symptoms, especially if they have signs of dehydration. Untreated dehydration in children can be fatal within a day.

A Quick Review

Stomach flu symptoms include watery diarrhea, nausea, vomiting, abdominal pain, and sometimes a low-grade fever. Babies and children with the stomach flu may have these symptoms, along with a lack of appetite.

Though the stomach flu may go away after a few days, it's important to watch for signs of dehydration that come with the illness. Dehydration and symptoms such as mental status changes and severe stomach pain require immediate medical care if you have the stomach flu.

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