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Vomiting, diarrhea, stomach cramps and nausea can leave you wondering what made you sick. When these come on suddenly, food poisoning or stomach flu are two common possibilities. The symptoms between the two conditions look very similar, but the timing and how you became sick can offer some clues as to what type of illness you’re experiencing.
Food poisoning happens when you eat or drink something contaminated with harmful germs or toxins. What people commonly call the stomach flu is usually viral gastroenteritis, an infection that affects your digestive system. Both conditions often improve on their own, although some symptoms can become serious if you become dehydrated.
Let’s take a closer look at food poisoning vs. stomach flu symptoms, causes and timing, plus when you should talk to a doctor.
The biggest difference between food poisoning and stomach flu is how you become infected. Food poisoning comes from consuming contaminated food or drinks. The stomach flu spreads from person to person or through direct contact with contaminated surfaces, people, or food and water.
The symptoms overlap between the two conditions, so you cannot always tell which one you have based solely on how you feel. The timing of your symptoms and whether other people around you are sick can provide useful clues.
| Food poisoning | Stomach flu | |
|---|---|---|
| Cause | Caused by contaminated food or drinks | Caused by a virus |
| When symptoms start | As soon as 30 minutes to several days after eating contaminated food, depending on the cause | About 12 to 48 hours after exposure to the virus |
| Symptoms | Nausea, vomiting, diarrhea and stomach cramps. Some types may also cause fever or bloody diarrhea. | Vomiting, diarrhea, stomach cramps, nausea and sometimes a low-grade fever or headache |
| Typical duration | About 1 to 2 days for many cases, though some infections can last several days or longer | About 1 to 3 days for most people |
These patterns can help you make an educated guess if you have food poisoning or stomach flu, but they do not necessarily confirm the cause. Several types of food poisoning can take days before symptoms appear, making it difficult to identify the food (or establishment that the food was served in) that caused the illness.
Food poisoning occurs when you consume food or a drink contaminated with harmful bacteria, viruses, parasites or toxins. Contamination happens during the growing, processing, preparation, storage or serving of foods and drinks.
Common causes of food poisoning include bacteria such as salmonella and certain strains of E. coli and parasites like Cyclospora. Toxins produced by bacteria also cause food poisoning.
Your symptoms may start fairly quickly after eating contaminated food or drinks, but that is not always the case. Symptoms of food poisoning include:
Some forms of food poisoning may cause bloody diarrhea or more severe symptoms. If you develop severe symptoms, check with your doctor rather than trying to manage them on your own.
The answer depends on what caused the food poisoning. Some types cause symptoms within a few hours, while others may take several days. That means the last meal you ate is not necessarily the source of your illness. A contaminated food you ate earlier in the day may be responsible, even if you felt fine afterward.
This is one reason it can be difficult to distinguish food poisoning from stomach flu based on timing alone. If several people who ate the same meal develop similar symptoms around the same time, food poisoning becomes more likely as the cause of illness.
The stomach flu is a common name for viral gastroenteritis, but it is not actually the flu (influenza). Influenza is a respiratory infection, while viral gastroenteritis affects your digestive system.
Several viruses can cause gastroenteritis, with norovirus and rotavirus being the most common ones. You can become infected with the stomach flu by having close contact with someone who is sick, touching a contaminated surface and then touching your mouth or consuming contaminated food or water.
Symptoms of the stomach flu include:
Because these viruses can spread easily, you may notice several people in your household, school, workplace or another group, such as on a cruise ship, becoming sick around the same time.
Most cases of food poisoning or stomach flu improve within a few days, but the exact timeline varies. Some types of food poisoning cause symptoms within hours and clear up within a day or two, while the stomach flu can last several days or longer. Norovirus, for example, one of the most common causes of viral gastroenteritis, typically causes symptoms for about one to three days.
Even after vomiting and diarrhea improve, you may not feel completely back to normal right away. Your appetite, energy level or digestion can take a little longer to return to normal.
Focus on getting enough fluids and slowly returning to your usual diet as you feel better. You do not need to follow an extremely restrictive diet while recovering. Choose foods you tolerate well and avoid anything that worsens your symptoms.
Cyclospora is a parasite that can cause a different intestinal illness called cyclosporiasis. The parasite thrives on fruits and vegetables, and several days after entering the intestinal tract, can cause significant abdominal discomfort, vomiting and “explosive diarrhea.” It does respond to antibiotics but symptoms can reoccur after treatment. Thorough rinsing, especially of lettuce of prior to ingestion, can minimize this infection.
No matter if you have food poisoning or the stomach flu, vomiting and diarrhea may cause you to lose more water, sodium (salt) and electrolytes than you may realize and you can become dehydrated.
Signs of dehydration include:
Aim to rehydrate slowly, taking small sips of water or an oral hydration drink, rather than gulping, as drinking too much too fast can be harder to keep fluids down and leads to more vomiting.
Sports drinks can also work for adults but should be diluted with water, due to their high sugar content, which can make diarrhea worse. Clear broths are another good option that provide both fluids and sodium. If nausea makes drinking difficult, ice chips or electrolyte popsicles may help.
Keep a close eye on young children, older adults and people with weakened immune systems as they can become dehydrated more quickly and could require medical attention sooner if vomiting or diarrhea is significant.
In many cases, rest and fluids are all you need while your body fights off the infection.
Over-the-counter medications may help with certain symptoms, like acetaminophen for a headache, body aches or fever reducer, but not all medications are appropriate for everyone.
For example, some anti-diarrheal medicines should be avoided if you have bloody diarrhea or a high fever. Children also have different medication considerations than adults.
Antibiotics do not treat the stomach flu and are not helpful for every form of food poisoning. Certain bacterial infections may require antibiotics, but that decision should be made with a health care professional.
If you take prescription medications or have another medical condition, check with your doctor before taking an over-the-counter medicine for symptoms like diarrhea or vomiting.
Related: What kills a stomach virus
Most cases of food poisoning or stomach flu resolve without medical treatment, but there are certain symptoms that require medical attention.
Contact your doctor if you have any of the following:
Need same-day care? Choose the care option that’s right for you.
While you cannot prevent every stomach infection, here are some healthy hygiene habits that can reduce your risk of contracting food poisoning or stomach flu:
Whether it’s food poisoning or the stomach flu, for most mild cases, the immediate priorities for an easy recovery are the same:
Pay attention to how you are feeling as you recover and listen to your body. If your symptoms persist or you feel you need an in-person evaluation, contact your provider or find same-day care near you.
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