10 Foods You Should Never Reheat in the Microwave—and Why

Even professional chefs swear by their microwaves, the ultimate rapid-heat renegade of the kitchen. From gently melting chocolate to steaming vegetables, warming soups, or crisping bacon, this little powerhouse delivers speed and precision without heating up the whole house. Microwaves revolutionized home cooking in the 1960s, saving cooks countless hours and spawning an entire industry of ready-to-heat meals for busy lifestyles. But as much as we love their convenience, not every food can handle their inside-out, supercharged heat. Whether facing soggy fries and rubbery bread or real safety hazards, there are ten foods you should never microwave.

How Microwaves Work

To understand why some foods suffer under microwave heat, it helps to know how this time-bending appliance actually works. Most conventional ovens use convection heat, circulating warm air to cook foods from the outside in. Toasters, toaster ovens, and broilers rely on short infrared waves that sear the food's surface, delivering quick browning and crisping while locking in moisture. Infrared waves don't penetrate deeply, so the food still cooks from the outside toward the center.

Microwaves, on the other hand, heat food from the inside-out. They emit microwave radiation— longer waves that penetrate deeply into the food—causing water, sugar, and fat molecules inside the food to vibrate rapidly. This generates heat from within—but not evenly. Depending on the food's composition, some areas heat up in a flash while others lag behind, leaving you with uneven results and dramatic hot spots.

Never Microwave In Plastic  

When it comes to plastic, the microwave isn’t your friend—it can leach chemicals into your food. Containers labeled "microwave-safe" only guarantee they won't melt or warp. This "safety" claim does not mean that they're safe for your health. 

When microwaved, plastics can break down and release chemical particles into food. A recent study from the University of Nebraska - Lincoln found that billions of micro- and nanoplastics are released into food and air during microwaving. Katia Savchuk of Stanford Medicine, notes in her recent article Microplastics and our health: What the science says that microplastics are "suspected to harm reproductive, digestive, and respiratory health and [suggest] a link to colon and lung cancer," as well as "a higher risk of heart attack, stroke and death."  

Instead of plastic, opt for microwave-safe glass or ceramic dishware—but be aware that microwaved vessels often get just as hot, if not hotter, than the food within them.

10 Foods To Never Reheat In the Microwave

Note, the USDA recommends all reheated leftovers reach 165 degrees to prevent foodborne illness.

Pizza

Though most college students would disagree, microwaving transforms pizza into flabby wedges with rubbery crusts. Steam from the sauce and toppings saturate the base, while the crust softens instead of crisping. It never gets the chance to crisp in this moist environment, so it ends up rubbery and limp.

How to reheat: Reheat pizza in the oven, or better yet, the air-fryer at 375 degrees.

Fried Food

Fried chicken nuggets, french fries, and hand pies all go limp in the microwave. Moisture trapped beneath the once-crunchy exterior destroys the crispiness, and oil redistributes unevenly, leaving food greasy, soggy, and sad.

How to reheat: Restore leftover fried food in a 300-degree oven on a wire rack.

Eggs

Hard-boiled eggs can explode when heated in the microwave. The heated moisture within turns to steam, building pressure inside the egg. With nowhere to escape, there's a real risk of a dangerous, messy explosion. Meanwhile, reheating scrambled eggs and omelets in the microwave results in rubbery disappointment.

How to reheat: Reheat hard-boiled eggs by steeping them in boiling water. For scrambled eggs, opt for gently reheating them in the oven, covered with aluminum foil to keep them moist.

Pasta

Leftover pasta fares poorly in the microwave. After sitting in the refrigerator, pasta absorbs moisture from its sauce, leaving the dish dry before it even reheats. The microwave then pulls out the additional moisture from the starchy noodles, making them tough and chewy. Uneven heating turns some clumps mushy and others hard and chewy.

Especially problematic in the microwave are pastas in cream-based sauces, from Alfredo to mac and cheese. Fats separate out from the liquid, leaving greasy pools and a curdled texture.

How to reheat: Instead of microwaving, reheat pasta gently on the stovetop with a splash of water (or milk for cream sauces) and stir frequently until warmed through. For plain, unsauced pasta, a quick dip in boiling water will revive it without compromising texture.

Casseroles 

Large casserole dishes are impractical for the microwave, and even smaller portions rarely heat evenly.

How to reheat: Sprinkle the casserole with a splash of water, cover with aluminum foil, and warm it in the oven at 350 degrees. The steam trapped by the foil will keep the dish moist while preventing the top from over-browning. Once heated through, remove the foil to re-crisp the top. Always check that the middle of the casserole has reached 165 degrees, this is where it will take the longest to heat up.

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Steak

Microwaves ruin a good steak, no matter how you cut it. The seared exterior turns soggy; any fat on the surface will heat unevenly, making it greasy and limp. The once-juicy interior jumps from warm to overcooked in mere moments, driving out its flavorful juices. Thick cuts are prone to uneven cooking, creating overdone edges and cool spots throughout. Instead, slice the steak thinly and briefly reheat it on the stovetop with a little oil.

How to reheat: Wrap the steak in aluminum foil and warm it in the oven at 350 degrees; finish with a quick stovetop sear over high heat to refresh the exterior crust.

Tacos

Flour tortillas turn rubbery, while corn tortillas crumble. Microwaving breaks down certain ingredients like vegetable shortening and the preservatives in store-bought tortillas, imparting sour, off-flavors.

How to reheat: Remove fresh toppings (like lettuce and sour cream), then bake leftover tacos at 375 degrees until heated through. Reassemble with the reserved toppings or add fresh ones for optimal texture.

Breads 

Microwaving bagels, flatbreads, and most other breads triggers starch retrogradation. The fast, uneven heat creates tiny pockets of boiling moisture, disrupting the starch network. The starches then swell, recrystallize, and collapse into dense hard spots, while other areas lose moisture and become tough and chewy.

How to reheat: To preserve texture, opt for the slower, outside-in warming of a toaster or oven. For crusty loaves, spritz them with water and wrap in aluminum foil before warming to keep them moist.

Spicy Peppers

Microwaving spicy peppers can be hazardous. When heated, their capsaicin—the compound that gives peppers their heat—vaporizes, creating a concentrated cloud of pepper-spray enclosed in the microwave. Opening the door releases these fumes, which can burn the eyes, throat, and lungs.

How to reheat: A safe method is to wrap spicy peppers in foil and heat in the oven at 350 degrees or slice and sauté them briefly on the stovetop.

Leftovers Over 4 Days Old

According to the USDA, "leftovers can be kept in the refrigerator for 3 to 4 days or frozen for 3 to 4 months." Beyond that, they lose both safety and quality. No matter the food, no microwave can rescue leftovers past its prime.