Upset stomach? It could have been that off-tasting salad—or it could have been a bug you caught at work. Stomach flu and food poisoning can have similar symptoms, but knowing the difference can help you determine how you got sick and if you’re contagious.

Board-certified physician Dr. Mitchell Forman explains stomach flu, food poisoning, and how to start feeling better no matter what you have.

Stomach Flu vs. Food Poisoning: What’s the Difference?

Viral stomach bugs and bad cases of food poisoning can have similar gastrointestinal symptoms—but there are some key differences between the two.

• Viral gastroenteritis (as called stomach flu, stomach bug, or a “24-hour bug”) is caused by a virus passed from person to person. Even though it’s called a “flu,” it’s not caused by the same influenza viruses we get flu shots for. There are also other kinds of gastroenteritis caused by parasites and bacteria.
• Foodborne illness (also called food poisoning) is caused by eating food that’s contaminated with bacteria, parasites, or a virus. Food can become contaminated when it’s not cooked correctly or handled safely.

Stomach Flu & Food Poisoning Symptoms

Both stomach flu and food poisoning can cause these symptoms:

• Nausea or vomiting
• Diarrhea that may be watery or even bloody
• Belly pain or cramps
• Fever
• Dehydration

Stomach flu can also cause chills and body aches. In most cases, people get sick about 1-2 days after being infected. Since stomach bugs are contagious, it’s important to limit your contact with other people to avoid infecting them.

For many food poisoning cases, symptoms can start appearing a few hours to a few days after eating contaminated food. Foodborne illnesses aren’t passed from person to person.

How do I tell the difference between stomach flu and food poisoning?

Since both illnesses can cause similar gastrointestinal problems, the main differences are how you got infected and how long it took for symptoms to appear.

It might be stomach flu if…

• You got sick 1-2 days after being around another sick person.
• Your child is sick, and other kids at school are sick, too.
• You got sick after spending a lot of time in close quarters with other people, such as at a church, dorm, school/daycare, nursing home, or on a cruise or airplane.

It might be food poisoning if…

• You got sick after eating at a new restaurant, café, or food truck.
• There are news reports of salmonella, listeria, or E. coli outbreaks in your area. (Check this page on the CDC website for current reports of foodborne illness outbreaks in the US.)
• You had meat or seafood that you suspect wasn’t fully done in the middle.
• Your salad included veggies or leafy greens that weren’t washed.
• You ate raw cookie dough.
• You ate food that was left out overnight.

Sometimes, you might have an upset stomach, nausea, or gas after eating something you know was prepared safely. Food allergies, a dietary fiber overload, and greasy/oily food can sometimes make people feel ill after eating. Those reactions may last a few hours to about a day.

If you can’t pinpoint why you’re sick and you’re concerned about your symptoms, call a doctor or visit an urgent care center.

Stomach Flu vs. Food Poisoning vs. COVID-19

Some stomach flu and food poisoning symptoms overlap with COVID-19 symptoms. But COVID-19 is often accompanied by respiratory problems, like trouble breathing and congestion, as well as severe fatigue, a sore throat, and the loss of taste or smell.

If you’re having any symptoms of COVID-19, follow these steps:

1. Stay at home and wear a mask when around family members or roommates.
2. Call an urgent care center or your primary care provider. Tell them about your symptoms. They’ll give you instructions on what to do and how to keep yourself and others safe.
3. Get a COVID-19 test. Contact your local pharmacy to schedule a test or learn more about tests on the CDC website.
4. Monitor your symptoms. Call a doctor right away if you or someone in your household starts having trouble breathing or has any other symptom that’s new or worsening.

At-Home Treatment

Most cases of stomach flu and food poisoning will clear up on their own in a couple of days. In the meantime, there are some things you can do to feel more comfortable at home:

• Stay hydrated. Vomiting and diarrhea make it easy to get dehydrated. Drink plenty of water in small sips. You can also try electrolyte replacement drinks or powders.
• Stay at home and rest. Getting plenty of rest can help you feel better. Don’t exercise or participate in any strenuous activity. If you have a stomach bug, you should also stay at home to avoid infecting friends or coworkers.
• Eat easy-to-digest foods. If you can handle them without feeling sick, try eating bland foods like saltines, applesauce, or bananas. Avoid alcohol and greasy, fried foods.
• Take over-the-counter medicine. Medicines containing acetaminophen (like Tylenol®) can help relieve pain and reduce fevers. Antidiarrheals (like Imodium® or Pepto-Bismol®) can help with diarrhea. Be sure to follow the instructions on the label.

When to See a Doctor for Stomach Flu or Food Poisoning

You should go to a doctor if you don’t start to improve after 3 days or if you experience any of these “red flag” symptoms:

• A fever over 102°F
• Vomiting that lasts longer than 2 days
• Diarrhea that contains blood or pus
• Trouble keeping water down
• Signs of severe dehydration (dry mouth, feeling dizzy, and/or decreased urination)
• Blurry vision or muscle weakness

In cases of severe dehydration, doctors can use an IV to replace lost fluids. They might also prescribe an antibiotic if you have a bacterial infection.

Dr. Forman urges patients to seek medical attention if they’re ever concerned about symptoms or the length of their illness. Visit a Florida Medical Clinic Urgent Care in Zephyrhills or Wiregrass, or call ahead at (813) 929-3600 (Wiregrass) or (813) 715-0374 (Zephyrhills).

About Mitchell Forman, MD

Dr. Mitchell Forman is certified by the American Board of Family Medicine and serves as Medical Director for the Florida Medical Clinic urgent care facilities in Zephyrhills and Wesley Chapel. As an urgent care physician, he treats all patients with compassion and care for all kinds of injuries and illnesses.

Disclaimer: This blog is not intended to substitute professional medical advice. Always talk with your doctor before starting or stopping medications or treatments.