When Do Your Leftovers REALLY Need to Be Tossed?

While leftovers make dinner so much simpler and we’re all about #mealprep, using the wrong containers or leaving food in the fridge for too long can either land you on the porcelain throne or in the hospital. So how do you know when you’re safe to get your grub on?

Regardless of what kind of leftovers are chillin’ in your fridge, they’re only good for four days. “We like to think of putting food in the fridge as pressing pause on its lifespan,” says Jennifer McEntire, Ph.D., vice president of science operations for the Grocery Manufacturers Association. “But it’s really only slowing down microorganism growth in your food.” (Case-in-point: Listeria, one of the most dangerous of these microscopic little buggers, grows just fine in the refrigerator.)

So assuming your refrigerator is the proper temperature—40 degrees Fahrenheit, says McEntire—four days is your max for keeping leftovers. And if you’re meal-prepping an entire week’s worth of food, put the second half of the week’s meals in the freezer and thaw them when you’re ready to eat them.

Follow these other tips to make sure you’re doing the whole “Tupperware for days” thing right and not blowing your grocery budget:

1. Don’t Leave Your Food Chillin’ on the Counter While You Netflix
You just made a huge pot of soup, so it needs plenty of time to cool before you pack it all up, right? Nope.

“If food sits out at room temperature for more than two hours, it’s susceptible enough to bacteria that you shouldn’t eat it,” says Marianne Gravely, technical information specialist for the Food Safety and Inspection Service with the USDA. Divide that soup (or whatever it is!) up, and get it in the fridge as soon as it’s done, even if it’s still hot.

This goes for your brown-bag lunch, too. Even if food is sealed up in a container, leaving it in your purse until lunchtime is a no-go.

2. Size Matters (and Small Is Better)
Gravely recommends using small storage containers. “You want to get your food down to the safe temperature of your fridge as quickly as possible,” she says. And the smaller the container, the faster your food cools. “Look for something two inches tall or shorter,” says McEntire.

3. Don’t Reuse Random Containers
It’s tempting to reuse that old giant Greek yogurt container to stash leftovers in, says Gravely, but it wasn’t made to be reused, and it won’t maintain your food like plastic or glass storage containers meant for the job.

Drop the few dollars on proper containers. They make for better #mealprep photos, anyway.

4. If You’re Going to Reheat It, Turn Up the Temp
Pulling your lasagna out of the microwave and realizing that the middle is still cold isn’t just a taste bud downer; it can actually be risky.

The USDA calls temps between 40 and 140 degrees Fahrenheit the “danger zone” because they’re an a-okay breeding ground for bacteria and microorganisms.

“You need every bit of those leftovers to hit 165 degrees,” says McEntire. While you might not feel like whipping out your food thermometer every time you nuke something, give your food a stir halfway through reheating it. Then let it sit for a minute or two before digging in, which will give the heat a chance to distribute through your meal.

Little kids and the elderly—and anyone with a compromised immune system—are more at risk for getting sick from bacteria in food, so McEntire recommends using the food thermometer before they nosh on reheated leftovers.