How long leftovers can safely stay in your refrigerator depends on the type of food and whether or not your fridge is truly keeping foods cold. It certainly saves you time and money to use leftover vegetables in a pasta or soup the next day, or leftover steak in a green salad. Err on the side of caution and safety, however, when dealing with leftovers in your fridge.

Leftovers stay safe only if you follow safety guidelines. Ensure that your fridge is between 32 and 40 degrees Fahrenheit. If the leftovers have already been out of the fridge for longer than two hours, err on the side of safety and toss them out. Place hot leftovers, such as soups or chilis that have been simmering on the stove, into shallow containers so they will cool within the two-hour safety period. Don't worry about putting hot foods in the fridge; you won't harm your refrigerator by doing so and you will cool the food more quickly.

Most leftover foods, including cooked meats, pizza, soups, stews, vegetables and stir-fries, last from three to four days in the refrigerator, according to the U.S. Food and Drug Administration. Foods that you or others have eaten directly from the jar or carton, such as baby food or cartons of Chinese food, are safe for only two to three days, because traces of saliva can promote bacteria growth. Make a habit of removing food to a separate container for eating if you plan to refrigerate the leftovers.

Some leftovers can last for almost a week in the refrigerator. Tomato-based pasta sauces, for instance, are so acidic that they last as long as five days once they are opened. Either frosted or unfrosted cakes also are safe for five days. Cover a cake with foil to avoid aromas from other foods from penetrating the cake. Check used-by or expiration dates on all products and follow those guidelines to keep food safe.

Despite the fact that refrigeration slows bacteria growth, some harmful bacteria may remain in leftovers. If you don't reheat food to at least 165 F, you may be at risk. Problems may occur when you reheat in the microwave, because cool spots might still exist in the foods. Minimize reheating problems by stirring the food halfway through heating and letting it sit for a minute or two so the residual heat is absorbed throughout the food.