Food Poisoning vs. Stomach Flu: What Are the Differences?

Identifying the cause can help you find treatment

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When you have symptoms that could be food poisoning or stomach flu, it can be hard to figure out which one you have. They both cause symptoms like vomiting and diarrhea. But these two conditions have completely different causes.

You get food poisoning from eating food contaminated with bacteria, viruses, or parasites. Stomach flu (medically known as viral gastroenteritis) is usually caused by contact with certain viruses.

This article explains the symptoms, causes, diagnostic tests, and treatments for food poisoning vs. stomach flu.

Tips to Prevent Food Poisoning - Illustration by Joules Garcia

Verywell / Joules Garcia

Symptoms of Food Poisoning vs. Stomach Flu

The symptoms that occur with food poisoning and the stomach flu overlap quite a bit, so it’s important to understand the signs specific to each condition.

The biggest difference between the two illnesses is in the timing:

  • If you develop symptoms within a few hours of eating, it’s likely to be food poisoning.
  • Stomach flu symptoms typically appear within a day or two after exposure to the virus.

Symptoms of Food Poisoning

The primary symptoms of food poisoning are:

  • Vomiting
  • Diarrhea (may be bloody, watery, or mucus-like)
  • Nausea
  • Stomach pain and cramping
  • Fever
  • Weakness

Get medical attention for:

  • Bloody diarrhea
  • Temperature over 102 degrees Fahrenheit (by mouth)
  • Inability to keep liquids down
  • Diarrhea that lasts more than three days

Symptoms of Stomach Flu (Viral Gastroenteritis)

The primary symptoms of stomach flu include:

  • Vomiting
  • Diarrhea (may be watery)
  • Nausea
  • Stomach pain and cramping
  • Fever
  • Chills
  • Headache
  • Muscle aches

Get medical attention for:

  • Change in mental state (e.g., irritability, lack of energy)
  • Diarrhea lasting more than two days
  • High fever
  • Frequent vomiting
  • Six or more loose stools in one day
  • Severe abdominal or rectal pain
  • Black, tarry, or pus-containing stools

Watch for Dehydration

Dehydration is a possible result of vomiting or diarrhea that lasts for more than 24 hours. Symptoms of dehydration include:

  • Dark or infrequent urine
  • Dry mouth
  • Dizziness
  • Weakness
  • Confusion
  • Fainting
  • High fever

Causes of Food Poisoning vs Stomach Flu

You can contract food poisoning and the stomach flu from exposure to germs, but in different ways.

Causes of Food Poisoning

Food poisoning is caused by eating something that’s contaminated with germs. This is usually bacteria like E. coli (Escherichia coli), Staphylococcus aureus, or Salmonella, but it can also include viruses or parasites.

With food poisoning, you'll notice that the illness:

  • Typically occurs within hours
  • Can be traced to a particular food source
  • Affects more than one person
  • Has more severe symptoms than the stomach flu (such as bloody diarrhea and projectile vomiting)

Causes of Stomach Flu

The stomach flu is an infection that attacks your intestines. It’s most often caused by viruses like norovirus in adults or rotavirus in children. But it can also be triggered by other viruses, bacteria, parasites, or toxins.

While other illnesses are transmitted through the air, the stomach flu is transmitted via:

  • Contaminated food or drink
  • Touching a surface that's been infected
  • Person-to-person contact with an infected person
  • Contact with the vomit or stools of an infected person

Not Really The Flu

The so-called stomach flu isn't related to the actual flu, which is a respiratory illness caused by an influenza virus.

Diagnosis of Food Poisoning vs Stomach Flu

A medical diagnosis of food poisoning vs. stomach flu isn't always necessary, but there are some exceptions.

You should see a healthcare provider right away for diagnosis and treatment if you're:

  • An older adult
  • Pregnant
  • Immunocompromised
  • Having severe or long-lasting symptoms

Most healthy adults don't need an official diagnosis. But a diagnosis can help steer you toward the right treatments and let you know if you're contagious.

Diagnosis of Food Poisoning

If you see a healthcare provider for suspected food poisoning, you can expect:

  • A review of your symptoms
  • Going over your medical history
  • Physical examination
  • Blood, urine, or stool tests to identify the potential source of infection

Testing is especially important in the case of a community outbreak.

Diagnosis of Stomach Flu

If you go to a healthcare provider with a suspected case of stomach flu, you should expect:

  • A review of your symptoms
  • Going over your medical history
  • Physical examination
  • Questions about your recent whereabouts since you're more likely to contract the illness in crowded places like daycares or cruise ships

Testing may not be done unless there's a reason to find out the strain of the virus, such as a viral outbreak in a hospital setting.

If needed, stool tests can be used to diagnose rotavirus, but this isn’t routine. Blood tests or imaging tests would only be performed if another disease or condition is suspected.

Common Infections

Each year in the United States, an estimated 48 million people get food poisoning, and up to 21 million people get the stomach flu from norovirus. Combined, they're responsible for thousands of ER visits and hospitalizations per year.

Treatment of Food Poisoning vs Stomach Flu

Treating food poisoning and the stomach flu involves similar tactics. As with many viruses, treatment focuses on preventing dehydration and managing symptoms.

For most people, this can be done effectively at home. Treatment options include:

  • Staying hydrated with fluids like water or electrolyte-rich drinks
  • Slowly incorporating a BRAT diet (banana, rice, apple, and toast) when you're able to keep food down
  • Getting plenty of rest to help your body heal
  • Using over-the-counter medications like Pepto-Bismol (bismuth subsalicylate) for an upset stomach, Imodium (loperamide) for mild diarrhea, or Tylenol (acetaminophen) for a fever
  • Taking prescription medications like Zofran (ondansetron) or Reglan (metoclopramide) to treat symptoms of nausea and vomiting, if recommended by your healthcare provider

In certain cases of severe food poisoning, your provider may prescribe antibiotics for infections like shigellosis or an antiparasitic for infections caused by parasites.

Are You High-Risk?

Immediate medical treatment may be required for babies, children, and people with compromised immune systems who are at high risk for dehydration from vomiting or diarrhea. Some cases of dehydration need to be treated with medications or intravenous (IV) fluids.

Prevention of Food Poisoning vs Stomach Flu

Food poisoning generally isn't contagious from person to person in the way that the stomach flu is, so prevention tips for both illnesses will vary a bit.

Preventing Food Poisoning

Food poisoning generally isn’t contagious, though some forms can be spread through contact with an infected bodily fluid (like when you touch contaminated feces and then touch your mouth).

To prevent food poisoning, you can:

  • Wash your hands and work surfaces before, during, and after preparing food.
  • Separate raw meat, poultry, seafood, and eggs from ready-to-eat foods.
  • Cook food to the right internal temperature to kill harmful bacteria.
  • Keep your refrigerator at 40 degrees F or below.
  • Refrigerate leftovers within two hours of cooking.

Preventing the Stomach Flu

The stomach flu is very contagious and easily transmitted. You can be contagious before symptoms appear and for days after they've gone away. The germs can stay in your stool for two weeks, as well.

To prevent transmission, you can:

  • Wash your hands often and well with soap and water. 
  • Keep your hands away from your mouth and avoid shaking hands during known viral outbreaks.
  • Handle and prepare food safely.
  • Clean and disinfect common surfaces.
  • Wash laundry thoroughly.
  • Stay home and away from other people when you're sick.

Summary

Food poisoning and the stomach flu can come with similar symptoms, like nausea and vomiting, but they’re different conditions. Food poisoning is caused by food that's contaminated by bacteria, viruses, parasites, or toxins. The stomach flu is usually caused by norovirus.

Both can typically be treated at home with hydration, over-the-counter medications for symptom relief, and rest. Protect yourself, your loved ones, and your community by practicing good hygiene habits and ensuring foods are prepared and served safely.

If you develop either condition, watch for signs of dehydration. See a healthcare provider if you have a weak immune system, are pregnant or elderly, or you have severe or lingering symptoms.

Frequently Asked Questions

  • What lasts longer, food poisoning or stomach flu?

    Food poisoning usually goes away in two or three days. Stomach flu from norovirus infection usually clears up in between one and three days.

  • Does influenza cause stomach problems?

    It can, especially in children. However, influenza ("the flu") is a respiratory infection similar to the common cold. "Stomach flu" isn't related to the influenza virus and is actually called viral gastroenteritis.

17 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Cristina Mutchler
Cristina Mutchler is an award-winning journalist with more than a decade of experience in national media, specializing in health and wellness content.