The stomach flu, medically referred to as viral gastroenteritis, is an infection that inflames the gastrointestinal (GI) tract. It affects the organs involved in digestion—from the mouth and esophagus to the stomach and intestines. This highly contagious illness is caused by viruses like norovirus or rotavirus.

Symptoms of the stomach flu can appear quickly after exposure—sometimes within just a few hours. While they may begin mildly, symptoms often worsen before improving. Most cases last fewer than seven days, and symptoms typically ease after the third day.

Stomach Flu vs. Influenza

Despite its nickname, the stomach flu is not the same as influenza. While influenza targets the respiratory system, viral gastroenteritis primarily affects the GI tract. Norovirus is the most common culprit, accounting for millions of cases annually in the U.S.

Nausea

Nausea is often one of the first and most noticeable symptoms. It can result from cramping, inflammation of the stomach lining, or other GI disruptions caused by the virus. Associated signs may include sweating, excess saliva, appetite loss, and weakness.

tips for relief:
Lying still may reduce nausea. When ready to eat, consider the BRAT diet—bananas, rice, applesauce, and toast—which is gentle on the stomach.

Vomiting

Many people experience vomiting with the stomach flu. It can begin 12 to 28 hours after infection and may continue for several days.

why it matters:
Repeated vomiting makes it hard to stay hydrated and can lead to electrolyte imbalances. These minerals, such as sodium and potassium, are crucial for regulating hydration and bodily functions.

ways to manage:
Avoid solid foods, sip clear fluids like water or electrolyte-rich drinks, and rest as much as possible.

Diarrhea

Diarrhea is another hallmark symptom, typically causing frequent, loose, or watery stools. The virus disrupts the intestine’s ability to absorb water and nutrients.

duration:
Symptoms often improve within a week. However, diarrhea lasting more than two weeks may signal another condition and requires medical attention.

important to know:
Severe or bloody diarrhea, or dehydration symptoms like dizziness, dry mouth, and fatigue, should be evaluated by a healthcare provider.

supportive care:
Drink fluids, eat bland foods, and consider probiotics to restore gut balance.

Dehydration

Dehydration occurs when fluid loss from diarrhea and vomiting isn’t replenished. It’s a common complication of stomach flu, especially in children and older adults.

signs of dehydration include:

  • Dark urine

  • Lightheadedness

  • Fatigue

  • Dry mouth

  • Thirst

  • Irritability

  • Rapid heartbeat

how to prevent it:
Drink plenty of fluids, including water and oral rehydration solutions like Pedialyte. Introduce bland foods gradually once you can tolerate eating again.

Abdominal Pain

Inflammation from the virus can cause stomach cramping or general abdominal discomfort. This pain is typically spread across the stomach rather than isolated in one spot.

when to worry:
If the pain becomes intense or persists beyond a couple of days, consult a healthcare provider. Severe pain upon touch may indicate a more serious issue.

management:
Initially avoid solid foods, then slowly reintroduce bland items like toast or rice. Hydration and rest also help.

Headache

Headaches during the stomach flu can result from dehydration, electrolyte imbalances, or fatigue.

how to relieve it:
Hydrate, rest, and use over-the-counter pain medications like ibuprofen if necessary.

Muscle Aches

Your body’s immune response to the viral infection may cause muscle soreness or myalgia.

how to feel better:
Muscle pain often improves with rest, hydration, and light stretching. It usually subsides within a few days.

Fatigue

Fighting off infection takes energy, which can lead to extreme tiredness or fatigue. This is your body’s way of signaling the need for rest.

tip:
Listen to your body and avoid exertion while recovering. Resting can speed up healing and lessen overall fatigue.

Fever

A mild fever (usually under 102°F or 39°C) is common during the stomach flu. It’s part of your body’s inflammatory immune response to the viral infection.

what helps:
Fever typically resolves with hydration, rest, and OTC fever reducers. Seek medical help if your fever exceeds 102°F.

Stomach Flu Symptoms in Children

Young children may not be able to communicate their symptoms clearly, and they’re more susceptible to complications from the stomach flu, including dehydration.

call a provider if your child has:

  • Persistent vomiting or diarrhea

  • Dark or bloody stools

  • Diarrhea lasting over 24 hours

  • High fever

  • Abdominal or rectal pain

  • Unusual irritability or fatigue

  • Low energy or activity levels

Signs of Dehydration in Children

Dehydration can progress quickly in infants and toddlers, especially when vomiting or diarrhea continues for more than a day.

warning signs include:

  • Dry mouth

  • No tears when crying

  • Dry or cracked lips

  • Fewer than six wet diapers per day

  • Sunken eyes or cheeks

  • Cool hands and feet

  • Fatigue or extreme fussiness

  • Rapid breathing

If these signs appear, contact a healthcare provider. Hospitalization may be needed to prevent further complications.

When to Contact a Healthcare Provider

Although viral gastroenteritis is usually self-limiting, it can sometimes lead to more serious issues. Contact a medical professional if you experience:

  • Diarrhea lasting longer than two days

  • Frequent vomiting

  • High fever

  • Bloody or black stools

  • Severe or persistent abdominal pain

  • Changes in mental state, such as confusion or drowsiness

  • Signs of dehydration

High-risk individuals—including pregnant people, seniors, and those with autoimmune disorders—should be especially cautious.

Signs of Severe Dehydration

If left untreated, dehydration may become life-threatening. Seek immediate medical care if you experience:

  • Confusion or disorientation

  • Extremely low urine output

  • Very dry mouth and skin

  • Fainting or loss of consciousness

  • Weak or absent pulse

  • Difficulty breathing

Questions to Ask Your Provider

Prepare for your visit by writing down questions such as:

  • What can I eat to reduce diarrhea?

  • Are there treatments to speed up recovery?

  • How can I avoid spreading the virus to others?

  • When is it safe to return to work or school?

A Quick Review

Stomach flu, or viral gastroenteritis, is a common viral illness that affects the GI system and causes symptoms like nausea, diarrhea, and cramping. Most people recover within a few days, but dehydration and other complications can occur—especially in children and immunocompromised individuals.

Rest, fluids, and bland foods are usually enough to recover. If your symptoms persist or worsen, seek guidance from a healthcare provider.