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How do I Tell the Difference Between Food Poisoning and Stomach Flu?

Mary McMahon
Updated Feb 05, 2024
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The distinction between food poisoning and the so-called “stomach flu” is actually a bit difficult to define, primarily because the term “stomach flu” is not really an accurate description. In both cases, the symptoms are very similar, and so are the treatments, since the condition often runs its course without medical intervention. Medical help should be sought if symptoms persist for more than 24 hours, or if they become extreme.

Food poisoning, also known as food borne illness, is caused when food becomes contaminated with something which is harmful, such as a bacteria, virus, or toxin. It can be the result of poor sanitation or improper food handling, and symptoms can emerge between two and 24 hours after eating, depending on the agent which causes the condition. Headache, fever, and fatigue often emerge first, followed by nausea, vomiting, stomach cramping, and diarrhea.

The key sign that gastrointestinal distress may have been caused by food poisoning is the presence of other people who ate the same thing and also became sick. If everyone becomes ill after a family meal cooked at home, for example, then the meal should come under suspicion. Food poisoning can be a bit trickier to narrow down when people eat at a restaurant, as the symptoms can take some time to emerge. For example, if people get sick two hours after dinner at a restaurant, dinner might not be the cause; it might have been the fruit everyone had at lunch.

The “stomach flu” is not actually a flu at all, since flu is caused by the influenza virus, which attacks the respiratory system. More properly, stomach flu should be known as gastroenteritis. It is caused by a viral infection of the intestines which causes irritation, and symptoms very similar to those above: nausea, vomiting, fever, diarrhea, fatigue, and chills. Gastroenteritis can be caused by consuming contaminated food, or by being exposed to a virus through poor sanitation. Food is the most common vector for gastroenteritis, so one could think of the stomach flu as a special subset of food poisoning.

In either case, the best thing for the patient is staying hydrated and resting. The symptoms will usually pass within 24 hours, although the patient may feel a bit weak for several days afterwards. Eating bland foods can also help, as can drinking products specifically designed for people with diarrhea, like Pedialyte and other fortified beverages which offer nutrition in addition to hydration.

If the symptoms persist or the patient starts vomiting or excreting blood or developing an altered level of consciousness, it is time to see a doctor. The doctor can narrow down the cause and prescribe a medication to deal with the virus, bacteria, parasite, or toxin which is causing the condition. It can be helpful to know what the patient has eaten in the last 48 hours, as certain foods are more prone to contamination than others; if the patient had chicken, for example, campylobacter and salmonella would be leading suspects.

WiseGeek is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Mary McMahon
By Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a WiseGeek researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Discussion Comments
By anon951318 — On May 15, 2014

Sunday morning I woke up with a bad headache. I took meds and hoped it would go away. I rarely have a headache. That afternoon after biting into a cookie, I felt sick to my stomach. The headache came on with a vengeance. I laid down and literally couldn't get it. The next morning, I threw up. I could barely walk. I was so dizzy that I couldn't even sit up.

The first two days, I had a wicked headache. It is four days later, and still I am not able to eat. My stomach feels like it has been punched. I have been eating watermelon the last two days.

I don't feel well, but now at least I'm up a bit. I'm not sure when I' can eat. My stomach is sore, and also my throat (throat box area). I have a dry cough but no congestion or fluid. I'm not sure if I have the stomach bug or food poisoning. How long do they last? When does not eating become a concern? The doc things stomach flu. Not sure.

By anon341986 — On Jul 16, 2013

Sometimes people actually have sensitivities or allergies to certain foods, but don't know it. Food poisoning is always a possibility when eating at restaurants, but it may also be possible that the restaurant used an ingredient that triggered an allergic reaction. When I worked in buffet-style restaurants, some people would have all the symptoms of food poisoning after eating fried chicken. Truth be told, I'd also get similar symptoms if I ate fried chicken during my lunch break. The managers tried to figure out if the chicken itself was spoiled, or improperly stored, or whatever. There was nothing obvious that would mean bad chicken, and the frying process should have killed anything like salmonella. We finally figured out that the chicken marinade included some ingredients like MSG, and a lot of people are sensitive to that ingredient. When we switched marinade brands, most of the complaints stopped.

It's been my experience that a stomach ailment due to indigestion or a virus can develop at any time, even if the person didn't eat anything potentially hazardous. True food poisoning has a tendency to show up a few hours after a meal.

By anon331962 — On Apr 25, 2013

I just ate a sandwich from a restaurant about an hour ago and within 30 minutes I felt very sick and weak then started vomiting very violently and had diarrhea immediately following. I feel much better now that everything is out so I'm sure it was from eating that sandwich that was probably sitting out too long before they served it.

By anon318964 — On Feb 10, 2013

So from the age of 14, I have had stomach problems. Sometimes I thought it was something that I ate or that i had the stomach flu. I had gas but instead of coming from my anus it came from my mouth. I was burping up this rotten egg smell, I had nausea, vomiting and diarrhea. My doctor prescribed a suppository (promethazine) to calm my stomach and it did, but it also made me drowsy so I could sleep until the bacteria was out of my stomach. The next day I was sore and exhausted. Is that called intestinal gas? I get it occasionally. What causes that?

By wavy58 — On Nov 08, 2012

@shell4life – It is possible to have the stomach flu and no diarrhea, though I think it's pretty rare. Symptoms are different for everyone.

I had the stomach flu with diarrhea and no vomiting. My husband caught it not long afterward, but he had vomiting and diarrhea.

When people have food poisoning, vomiting and diarrhea usually occur together so that the body can rid itself of the toxin as quickly as possible. With all of that waste leaving the body so rapidly, I think that people with food poisoning are more at risk of dehydration than people with the stomach flu.

I've also heard that many times with the stomach flu, the vomiting will happen for a day or so, and then the diarrhea will arrive, or vice versa. It's like they wait their turn, so your body isn't quite so overwhelmed.

By shell4life — On Nov 08, 2012

I know that with food poisoning, you have diarrhea, but is it possible to have the stomach flu without diarrhea? I've been sick before with vomiting every hour or so but I didn't have any problems with diarrhea. Was this the stomach flu or something else?

By OeKc05 — On Nov 07, 2012

If you get food poisoning symptoms after eating at a restaurant, it can be hard to prove it was caused by the food, unless you dined with someone who ordered the exact same thing as you. I know that just about every time I eat out, my friend orders something entirely different from what I'm having.

There's really no way to know if the sickness was brought on by a virus or a toxin in the food. I suppose that since the treatment for both is basically the same, it doesn't really matter.

It would be nice to be able to alert the restaurant that their food is making people sick, but probably by the time you realized you had food poisoning, it would be too late. Many people would have already eaten the contaminated food, and it could all be gone by that point.

By StarJo — On Nov 06, 2012

@clintflint – I'm from Mississippi, and everyone around here calls it the “stomach virus.” I rarely hear the term “stomach flu.” Since gastroenteritis is often caused by a virus, this is pretty accurate, except in the case where it is caused by bacteria instead.

By Mor — On Nov 03, 2012

I lived in a third world country for a while and I had food poisoning a few times there. Although, to be perfectly honest, the worst case was when I had a meal that had been cooked by other ex-pats, so I can't blame the locals.

Luckily, I realized why I was starting to feel extremely ill and I went and made myself vomit. I had never done that before and I felt awful, but I was still sick to the point where I couldn't move for two days. I hate to think of what would have happened if I hadn't made myself throw up before it got too bad.

I don't recommend doing that as a food poisoning treatment unless you know what you're doing though.

By pastanaga — On Nov 03, 2012

@anon163814 - While you will want to vomit if you've got appendicitis, you'll also have a high fever and generally be in a great deal of pain, particularly to the right side of your stomach (pain on the left side is usually gas).

Usually a person with appendicitis is going to be feeling sick enough to want to go to hospital anyway. If you've got someone that ill, it's possible that it's food poisoning, but you should take them to hospital regardless. Food poisoning can kill, particularly if the person is already sick, or is quite young or old.

By clintflint — On Nov 02, 2012

Apparently it's quite a bad thing that people are calling gastroenteritis the "stomach flu" so much now. It's easy to see why they started it, but now people associate the word "flu" with those symptoms (upset stomach and food poisoning-like symptoms) when it has nothing to do with those.

It's leading to people claiming the flu vaccines don't work, because they don't prevent the "stomach flu". Which means that doctors have to spend public money educating people on what the difference is, and why there was never a way for the vaccine to protect against feeling sick to your stomach, before they prevent people from getting the vaccine.

My family mostly calls it a "stomach bug" because, let's face it, no one is going to call it gastroenteritis. But stop calling it stomach flu.

By anon163814 — On Mar 29, 2011

how can you tell the difference between food poisoning and the need for a removal of an appendix?

By anon135038 — On Dec 16, 2010

I had Japanese sushi with my husband the night before the next day around 6:00 I got sick- then a few hours later my husband got sick with d- and throwing up too. I'm pregnant, so this was no fun getting sick every 15 mins which ended up behind stomach acid because nothing was left in my stomach.

I ended up going to the hospital because I needed some fluids and was worried that I would get cramps after that I got sick only once very little, and was fine the rest of the day eating crackers, rice and applesauce to help along with gatorade to rehydrate me

Being sick is no fun but now I'm scared to ever eat there again, even though we have eaten there a lot. I guess I'll try and eat more from home since I'm pregnant!

By anon130362 — On Nov 28, 2010

I do not know what I had. I was vomiting, no diarrhea, but weak and tiredness. I had Thanksgiving dinner then I got sick - about six hours later, but no one else in my family got sick.

By anon130234 — On Nov 27, 2010

I'm sick now, and none of us are sure what it is. we all had thanksgiving dinner, but only half of us are sick. the baby's sick, so I guess it's probably gastroenteritis. ugh.

By anon75815 — On Apr 07, 2010

i don't know what i have. i think it's food poisoning but im not really sure. I had two egg rolls from a gross chinese place in my town and i got home and like four hours later i threw it up six times for about eight hours then the next day i missed school and i didn't throw up but i have barely eaten anything since then. and i threw up once so far tonight. i have a slight fever, fatigue, nausea, vomiting, no diarrhea, dizziness, drowsiness, and weakness and tiredness.

can someone tell me what i have because i don't think it's that serious to go to the hospital/doctor.

By zoid — On Mar 22, 2010

I was sure that I had food poisoning a few weeks ago - within just an hour or so of having lunch, I got very sick to my stomach. After vomiting periodically for the following 24 hours, however, I think it was actually a norovirus. A lot of people I knew were suddenly getting sick, with really similar sudden symptoms.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a...

Learn more
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