Day-old pizza is safe to eat if it was refrigerated within two hours of being made or delivered. Left in the fridge at 40°F or below, pizza stays safe for three to four days. The real question most people are asking, though, is whether the pizza they left sitting on the counter overnight is still okay. That answer is more complicated, and the official guidance says no.
The Two-Hour Rule
Bacteria that cause food poisoning grow fastest between 40°F and 140°F, a range food safety experts call the “danger zone.” In that window, bacterial populations can double every 20 minutes. The USDA’s guideline is straightforward: perishable food should never sit out at room temperature for more than two hours. If the room is above 90°F (a hot kitchen in summer, for example), that limit drops to one hour.
Pizza qualifies as perishable because of its cheese, sauce, and especially any meat toppings. Once it crosses that two-hour mark on the counter, the official recommendation is to throw it away.
What If It Sat Out Overnight?
This is the scenario most people are really wondering about: you ordered pizza, ate a few slices, left the box on the counter, and found it the next morning. By strict food safety standards, that pizza has been in the danger zone for 8 to 12 hours and should be discarded.
That said, research looking at actual bacterial growth on pizza paints a slightly more nuanced picture. A study examining pizza held out of temperature control in university dining halls found that the real-world risk tends to become significant only after about eight hours at room temperature. The pathogen most likely to grow on pizza in those conditions is Staphylococcus aureus, and even under worst-case modeling (warm temperatures, favorable pH), its growth over several hours was relatively modest. The researchers concluded that pizza represents a “theoretical risk” that would most likely become an actual risk beyond eight hours.
That doesn’t mean overnight pizza is guaranteed to make you sick. Many people eat it without incident. But it does mean the risk increases the longer it sits out, and there’s no reliable way to tell from looking at or smelling a slice whether harmful bacteria have multiplied to dangerous levels. Staph bacteria, for instance, produce toxins that are heat-stable, meaning reheating won’t destroy them once they’ve formed.
Refrigerated Pizza Lasts 3 to 4 Days
If you get your leftovers into the fridge within that two-hour window, you have a comfortable margin. The USDA rates refrigerated pizza as safe for three to four days when stored at 40°F or below. After that, bacterial growth can reach unsafe levels even at refrigerator temperatures.
For the best results, store slices in an airtight container or wrap them tightly in foil or plastic wrap rather than leaving them in the open pizza box, which lets them dry out and exposes them to other fridge odors.
How to Tell If Pizza Has Gone Bad
Time and temperature are the most reliable indicators, but your senses can catch obvious spoilage. Visible mold, even a small spot, means the entire slice should be thrown away. A sour or “off” smell is another clear signal. Cheese or toppings that feel slimy to the touch, or dough that has turned grayish, both indicate spoilage. If anything tastes noticeably wrong, stop eating.
Keep in mind that dangerous bacteria often produce no visible signs at all. A slice can look and smell perfectly fine while harboring enough Staph or Salmonella to cause illness. So sensory checks are useful for catching obvious spoilage, but they can’t confirm a slice is safe.
Reheat to 165°F
When eating refrigerated leftovers, reheating to an internal temperature of 165°F kills most common foodborne bacteria. A skillet over medium heat for a few minutes (with a lid to melt the cheese) or an oven at 375°F for about 10 minutes both work well. Microwaving is faster but tends to make the crust rubbery.
One important caveat: reheating protects you from live bacteria, but it does not neutralize all toxins. If Staph bacteria had time to produce toxins before the pizza was refrigerated, those toxins survive reheating. This is why getting pizza into the fridge quickly matters more than how thoroughly you reheat it later.
What Food Poisoning From Pizza Looks Like
Staph food poisoning, the most common risk from pizza left at room temperature, hits fast. Symptoms typically appear within 30 minutes to 8 hours and include nausea, vomiting, stomach cramps, and diarrhea. Most cases resolve within a day or two without treatment.
Other bacteria that can grow on pizza toppings, like Salmonella or E. coli, take longer to cause symptoms (anywhere from 6 hours to several days) and can cause more severe illness including bloody diarrhea and high fever. These are less common from pizza specifically but possible, particularly with meat toppings that were undercooked or cross-contaminated.
Most healthy adults recover from mild food poisoning on their own. The greater concern is for young children, older adults, pregnant women, and anyone with a weakened immune system, who face higher risks of serious complications from the same bacteria.