Is It Safe To Eat Pizza That Has Been Left Out Overnight?

August 21, 2023
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Throwing Out Food Isn’t Great - But Food Poisoning is Worse

Sometimes we leave food out overnight and hate the idea of it being wasted. So it's very tempting to eat it especially when it looks perfectly fine.

Although it may still appear fresh and okay to eat, it's never a good idea to eat foods left out overnight. After a specific window, bacteria begin to make a new home on food like pepperoni pizza.

Depending on the type of bacteria, consuming spoiled foods can potentially land you in the hospital or cause a bout of chronic illness due to food poisoning.

About 48 million people get sick with food poisoning every year. Out of that number 128,000 cases are hospitalized and around 3,000 result in death.

Food poisoning can be prevented by keeping foods properly stored and keeping your cooking environment clean. Also, by ensuring you keep your hands washed and sanitized while preparing food.

On the flip side, sometimes food left out is safe to eat but only within a certain time. So, is it safe to eat pizza that is left out overnight? Let's delve a little deeper into why or why not.

Put that Pizza in the Fridge! Don’t Leave it On the Counter Overnight!

Leftover Pizza and Food Safety

Eating leftover pizza is always a treat, especially since it's one of the most accessible foods. A leftover slice of cold pizza is good at any time of the day. But what if you left it out overnight?

Generally, people think that if you thoroughly cook it, leaving pizza out overnight is no big deal, right? Wrong.

The USDA Two Hour Rule

Pizza left out overnight is prone to bacterial growth that cause foodborne illness. So, according to the USDA, it's best to toss any perishable food that has been out longer than two hours.

It's important to throw it away because harmful bacteria that cause foodborne illnesses thrive in temperatures between 40 degrees Fahrenheit and 140 degrees Fahrenheit. So it's always best to place pizza in the fridge to help maintain its freshness.

Pizza can last for about four days after refrigeration. Refrigerated pizza can still undergo bacterial growth - even at temperatures below 40 degrees Fahrenheit - although the growth is much slower than what occurs at room temperature. Eating it after around three or four days, however, could also spell trouble. So it's best to toss it if it's been in your fridge longer than four days.

Explanation of the USDA’s Two Hour Rule

Frozen Pizza

The same rules apply to frozen pizza. If it's been left to thaw for longer than two hours, the ingredients are prone to growing bacteria.

In this case, it may be more dangerous since the ice turns into water once it thaws. The moisture will easily promote the growth of bacteria.

Staph Bacteria and Food Poisoning

Staphylococcus aureus is a bacterium that causes food poisoning. Staph bacteria are present all around us in the environment and even reside on our skin.

Food becomes contaminated with staph if it's not stored correctly at the correct temperatures. If the storage environment is not hot or cold enough, this will create the perfect environment for staph bacteria to grow.

Eating Pizza That has Been Left Out Overnight is Likely to Make You Sick

It's important to note that staph bacteria can also produce toxins that you can't quickly kill by heat. So, even if you reheat contaminated food, it may kill the staph but not the toxins it creates.

Once ingested, these toxins can cause food poisoning. Symptoms of food poisoning include:

  • Nausea
  • Cramping
  • Vomiting
  • Muscle cramps
  • Headache
  • Diarrhea

The severity of symptoms can vary from person to person. It depends on how your body reacts to the toxins and how much-spoiled food you consume. Typically it takes a few days to recover; however, it can take up to 10 days depending on the severity of the illness.

What if Outside Temperatures Were Cold?

If you live in a cold environment or you're in a season where it's very frigid out, it may be safe to consume pizza left out overnight. This, however, depends on the actual temperature in the room.

If the room is 40 degrees Fahrenheit or less during the night, then it's safe to consume. But keep in mind that it needs to be 40 degrees or colder outside.

However, if it's higher than 40 outside, then don't take the chance. You still want to inspect the pizza and ensure it's okay to eat despite how cold it may be.

This is only okay if you live in very cold parts of the world. Otherwise, the 2-hour window rule applies in any other instance. It's always better to be safe than sick.

Does Reheating Pizza Kill Bacteria?

The theory that reheating food kills bacteria is known by many. But does it work?

The truth is that leftover cooked food left out overnight can sometimes be saved through reheating, but not always.

To effectively kill off bacteria, foods need to reach a core temperature of 140 degrees Fahrenheit.

Unfortunately, this isn't always the cause. For example, after developing on foods, some bacteria can create heat-resistant toxins.

So, as previously mentioned, do not reheat foods that have been left out unrefrigerated the past two hours. It's also important to remember to pay attention to any potential signs of spoilage, even if they are out within the two-hour window.

Ensure that there's no mold, bacteria, or odd smells. Also, make sure no discoloration has taken place on the toppings.

Best Ways to Reheat and Preserve Pizza

Preserving and reheating your pizza properly can help prevent any potential food poisoning. However, if you improperly store your pizza at the wrong temperature, it can cause it to spoil or just become stale.

Storing your pizza correctly can be done by placing it on a dinner plate, wrapping it with parchment paper, foil, or wax paper, and placing it in the refrigerator.

You can also opt for placing it in Tupperware or a similar airtight container prior to refrigeration. But, again, ensure the lid is tightly sealed and not to store too many pieces in one container. Putting too many pieces inside the same container will increase the chances of them becoming extra soggy.


In terms of freshness, there are ways you can properly reheat pizza that can keep that delicious flavor and crunch from when you first got it.


The oven can take some time depending on how many slices you reheat but it's well worth it. You will want to place the slices on a baking sheet and put the oven on 275 degrees Fahrenheit.

Put the time for 25-30 minutes, but you'll want to keep a close eye and check them now and then. If they are warming too slow, increase the temperature but be sure it's not too high.

Increasing up to 350 degrees should be high enough. If you don't want to use a baking sheet you can wrap the pizza in aluminum foil and place it directly onto the oven rack.

If it's at 350, leave it on the rack for 10 minutes. If you want extra crispy, leave it in a little longer.


Reheating on the stove is a great way to get the crust nice and crispy while melting the cheese to a gooey consistency.

To do this, you want to put the pizza in a skillet on the stovetop. Turn the heat to low and place a lid over the pizza. Let it reheat for about 6-8 minutes.

Once it's done, you'll have a warm and bubbly cheese with a perfectly crunchy crust.

Frank Salvatore

Hey there - I'm Frank Salvatore. I created this site as a comprehensive kitchen resource. You'll find everything you need to know about everything in your kitchen. From appliances to utensils and layout - it is covered on this site!

About Me
Frank Salvatore
I created this site as a comprehensive kitchen resource. You'll find everything you need to know about everything in your kitchen. From appliances to utensils and layout - it is covered on this site!
Learn More About Me
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