Even in this crazy world we live in today, there are few things in life quite as horrible as being knocked on your ass by a mystery illness. Sure, any kind of illness sucks, but when you aren't sure exactly what's wrong with you, it makes it kinda hard to treat things — or know if a trip to the doctor is in order. And when you're feeling gross with a stomach ache that won't quit, your head usually bounces between two possibilities: Food poisoning or the flu.

It's easy to get confused between food poisoning and the flu (especially when you are spending the majority of your day sprawled out on the bathroom floor or praying to the porcelain god), but there are actually some major differences in the symptoms between the two that make it easy to tell what might be ailing you.

More: How to Tell if You Have a Common Cold or a Full-Blown Case of the Flu

We got a symptom breakdown from Alysa N. Veidis, a family nurse practitioner at Boston Medical Center. Check the list below to decipher the meaning of each symptom and what to do about it.

1. Nausea

Nausea is one of the key symptoms of food poisoning. The FDA reports that the onset of food poisoning is anywhere from immediately after ingestion to 48 hours later, depending on the type of food and bacteria exposure. "If you have information or evidence that the food you ingested was tainted and you are having symptoms as described above, you should seek medical attention," says Veidis. (Use this handy-dandy chart to match up exactly what you ate with the time you can expect to be getting sick.)

2. Vomiting

Nausea's older brother, this unpleasant symptom is a sign that you have food poisoning. "Vomiting may also present itself [as a flu symptom], but that is more common in children than adults," Veidis says. "If you have blood in your vomit, make sure to get to a [health care] provider right away."

3. Chills

Chills are common when your body is fighting an infection such as the flu, according to MedicineNet. Chills are also a common side effect of fever, so make sure to take your temperature and try to ward off a potential fever by drinking lots of fluids.

4. Fever

Fever is another common side effect of the flu. "If you are having high, uncontrolled fevers, you should seek prompt medical attention," Veidis says. Adults should seek medical care for any fever above 103 degrees or a fever that has lasted more than three days, according to the Mayo Clinic.

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5. Sore throat

Cold-like symptoms, such as a sore throat, are often signs that your body is fighting the flu. According to Common Health, as of late March, flu season has not yet peaked, which means it's more important than ever to get your flu shot.

6. Runny nose

Another symptom typically associated with the common cold, a runny nose could actually be a sign of the flu when it's in conjunction with a sore throat, fever and body aches.

7. Stomach pain/diarrhea

If your symptoms are stomach-related, such as cramps, pain or diarrhea, chances are you have food poisoning. According to Veidis, children are more likely than adults to suffer from vomiting and diarrhea when they have the flu.

8. Fatigue

Fatigue, defined as "extreme weakness or tiredness that interferes with your normal activities," is another sign of the flu, one that is especially common in early onset. If you think you may be fighting the flu, Veidis says getting to the doctor within 48 hours is critical.

9. Body aches

Body aches are another early sign of the flu. Make sure to monitor your symptoms, and get to the doctor ASAP if your body aches coincide with symptoms such as fever or fatigue. Getting to the doctor within 48 hours will allow your provider to "assess next steps and advise you regarding treatment options, which could mean antiviral medication," Veidis says.

For both food poisoning and flu (and, let's be honest, for everything else, too) drink plenty of water, get lots of rest and call your doctor if you notice a spike in your fever.

Most importantly, try to find some way to enjoy that forced bed rest!

Originally published March 2016. Updated October 2017.