The 1 Sign You Should Never, Ever Ignore If You Suspect You Have Food Poisoning

If youve ever had food poisoning , you probably know the symptoms are far from pleasant.

Most of us look back on these bouts as a day-ruining experience that we desperately hope to avoid in the future, but for some populations, food poisoning can be dangerous.

I speak from personal experience: As a 9-month-old, I got salmonella from raw chicken. While I cant exactly say I remember it, my parents tell me I got so dehydrated I had to be hospitalized and lost 20% of my body weight. If its not obvious by now, I pulled through, but immunocompromised people such as infants, older people and pregnant women are especially at risk for serious, life-threatening complications.

With all of that in mind, what are the top signs of food poisoning? And when do symptoms warrant immediate medical attention? Heres what you need to know. 

The most common signs of food poisoning to know about and some lesser-known signs to watch out for, too

Its not something we like to talk about, but if youve ever had food poisoning, you can probably list a few of the symptoms it causes.

If not, gastroenterologist Andrew Boxer  can clear that up. By far the most common are nausea, vomiting, fever and diarrhea, he said. Many patients can also have generalized stomach upset.

According to Sam Martin, a senior director and food safety expert at Microbac Laboratories , other common symptoms can include headache, chills and sweating.

In rare cases, food poisoning can cause blurry or double vision, muscle weakness, or tingling, he said. 

The symptoms you experience depend on the type of bacteria causing them, Martin said.

Hundreds of bacteria, parasites and viruses can cause food poisoning. Depending on the culprit, symptoms and the time it takes to experience them will vary, he said. Symptoms can start as soon as 30 minutes from the time you consume contaminated food with S. aureus, which typically results in nausea, vomiting, cramps and diarrhea. Others will take a couple of hours, as is the case with salmonella, which causes fever, diarrhea, nausea, cramps and vomiting. Finally, it can take several days for E. coli symptoms to present, which are typically cramps and diarrhea, which is sometimes bloody.

All three of these bacteria can come from a variety of foods, from undercooked meat to veggies at a salad bar, so it can be hard to know which one you have based on what youve eaten recently. If youre trying to make a distinction among S. aureus, E. coli and salmonella, pay attention to the symptoms.

Is there a way to distinguish between food poisoning and a stomach bug?

Of course, diarrhea, vomiting and cramping arent always caused by food poisoning. Stomach viruses such as the norovirus can also be to blame. Is there a way to tell which is which?

The two biggest differences are how quickly symptoms start after exposure and how long the symptoms last, Martin said. Typically, the stomach flu takes 24-48 hours from the time of exposure for symptoms to occur, and those symptoms will last between three and five days. Food poisoning symptoms usually come on more quickly within 24 hours and only last for a day or two.

Its important to note that since so many different organisms cause food poisoning and the stomach flu, theres a lot of overlap in symptoms, Martin said. Telling the difference between the two can be difficult, he said. 

Boxer echoes this, saying that lab testing is the only real way to tell. This would be done in the form of stool studies, he said. 

The one sign of food poisoning you should never ignore

In some cases, food poisoning can be dangerous and require medical attention.

You should see a doctor immediately if you have bloody stool or diarrhea, Martin said. When food poisoning causes GI bleeding, its often a sign that its reached a more serious level. Other signs that you need medical attention include blood in your urine, a fever greater than 102 degrees Fahrenheit, slurred speech, blurry vision, or if any of your symptoms last more than three days.

Food poisoning is never pleasant, nor is it fun to talk about. While symptoms will usually pass on their own within a few days, thats not always the case. And knowing the more serious symptoms can quite literally save your life, so be sure to see a doctor ASAP if you start noticing more serious signs.