No, week-old pizza is not safe to eat, even if it has been in the refrigerator the entire time. The USDA recommends keeping leftovers for no more than 3 to 4 days in the fridge, and research on refrigerated pizzas specifically found they were “unacceptable” after 7 days at any refrigerator temperature, with significant bacterial growth appearing between days 8 and 10.
Why 3 to 4 Days Is the Limit
The USDA sets a clear window: leftovers, including pizza, should be eaten within 3 to 4 days of refrigeration or frozen for longer storage. This guideline exists because harmful bacteria can still grow slowly at refrigerator temperatures. Your fridge slows bacterial reproduction down, but it doesn’t stop it.
A study examining refrigerated pizzas found that the sensory shelf life (the point where the pizza looks and smells noticeably off) was about 5 days at 50°F and 6 days at 37°F. But the important detail is that dangerous bacteria like E. coli showed significant population increases between days 8 and 10, meaning the pizza becomes progressively more hazardous the longer it sits. By day 7, researchers classified the pizzas as unacceptable at either temperature.
It Can Look Fine and Still Make You Sick
The trickiest part of old pizza is that it may not show obvious signs of spoilage. You might not see mold or smell anything off, especially if the pizza has only been in the fridge for five or six days. But bacteria like Staphylococcus aureus and Bacillus cereus, both of which have been detected on pizza, can reach harmful levels before your nose or eyes notice anything wrong. S. aureus is especially concerning because it produces toxins as it grows, and those toxins cause illness even if the bacteria themselves are later killed by heat.
This is why the “smell test” is unreliable for food safety decisions. Your senses are good at detecting rot and mold, but they can’t detect the pathogens or toxins that actually cause food poisoning.
Reheating Won’t Fix It
A common assumption is that blasting old pizza in the oven or microwave will kill anything dangerous. Reheating leftovers to an internal temperature of 165°F does kill most active bacteria. But it does not destroy all bacterial toxins. S. aureus toxins, for example, are heat-stable. Once the bacteria have produced them in your pizza, no amount of reheating will neutralize them. So while reheating fresh leftovers within the 3-to-4-day window is a good practice, it’s not a safety net for pizza that’s been sitting for a week.
What Food Poisoning From Old Pizza Looks Like
If you do eat pizza that’s been around too long, the type of illness depends on which bacteria were present. The most likely culprit on old pizza is Staph food poisoning, which hits fast: nausea, vomiting, stomach cramps, and diarrhea within 30 minutes to 8 hours of eating. It’s intense but usually short-lived.
Clostridium perfringens, common in cooked foods held at unsafe temperatures, causes diarrhea and stomach cramps that typically resolve within 24 hours, with symptoms starting 6 to 24 hours after eating. E. coli, which researchers found growing on refrigerated pizza after about a week, can cause severe stomach cramps and bloody diarrhea 3 to 4 days after exposure and is a more serious infection.
How to Store Pizza Safely
Get leftover pizza into the refrigerator within two hours of it being served. If your kitchen or dining area is particularly warm, that window shrinks to one hour. The temperature danger zone for bacterial growth is between 41°F and 135°F, and pizza sitting on a counter falls squarely in that range.
Once refrigerated, plan to eat your leftovers within 3 to 4 days. If you know you won’t get to it that quickly, freeze it instead. Frozen pizza stays safe for 3 to 4 months, though the texture and taste will degrade over time. When you’re ready to eat refrigerated leftovers, reheat to 165°F (steaming hot throughout) to kill any bacteria that may have started growing during storage.
If your pizza has already been in the fridge for a full week, the safest move is to throw it out. The money you save isn’t worth the hours you could spend dealing with food poisoning.