What Temperature and How Long Should Leftovers Be Reheated?

For leftovers to be safe to eat, their internal temperature must reach at least 74°C / 165°F and stay at that temperature for at least 15 seconds; this threshold inactivates bacteria that may have grown during storage. Food heated only until it is “lukewarm,” without reaching this temperature, poses a risk of food poisoning. No matter which reheating method you use (stovetop, oven, or microwave), the key factor is the internal temperature reached, not the time; food can look hot on the outside while remaining cold in the middle. That is why times given in minutes are only a starting point; the definitive check is always whether the heat has reached the thickest part of the food.

How do you reheat food on the stovetop?
Liquid-heavy foods such as soup, sauce, or stew are heated over medium heat, stirring occasionally, until they come to a boil, which takes 5–8 minutes; boiling is the most practical sign that the internal temperature has passed the safe threshold. Stir thick foods, such as chickpea stew or vegetables with ground meat, more often to keep them from sticking, and add a few spoonfuls of water if needed. If only the edges are boiling while the center is still lukewarm, that is a sign the heat has not spread sufficiently.

How long does it take to reheat food in the oven?
The oven is a method that preserves the texture of casseroles and other baked dishes in particular: heat the food in an oven set to 180°C / 355°F, covered with foil, for 20–25 minutes. Uncover it during the final 5 minutes so the top can brown lightly without drying out.

How can you heat food evenly in the microwave?
Because a microwave heats food from the edges inward, a cold spot in the center of the plate is a common problem. Stopping to stir the food or rotate the plate every 2–3 minutes largely solves this problem. Making a small hole with a fork in the center of a thick portion also helps heat reach the inside more easily. Covering the food with a damp paper towel or a microwave-safe lid keeps moisture on the surface, preventing the food from drying out and helping the heat spread more evenly.

How many times can food be reheated?
Each heating-and-cooling cycle gives any remaining bacteria a new opportunity to multiply; that is why it is recommended that food be reheated only once, and that you heat only the amount you will eat at that sitting. Instead of repeatedly heating and cooling a large container of food, dividing it into single-use portions in storage containers greatly reduces this risk.

Why do rice and chicken need extra care when reheating?
Cooked rice left at room temperature may contain spores of a bacterium called Bacillus cereus, which reheating does not completely inactivate. For this reason, cool rice and put it in the refrigerator within 1–2 hours after cooking, and reheat it only once. For meat-heavy dishes such as chicken, inserting a food thermometer into the thickest part of a piece of meat is much more reliable than checking by sight to make sure the internal temperature has reached 74°C / 165°F. A chicken breast stored whole takes longer for heat to reach its center than one cut into thin slices, so slicing it before reheating is recommended. The same reasoning applies to the center of a thick meatball or a vegetable dish made with ground meat.