Glass is the only safe answer.

Glass is the safest thing you can reheat food in, full stop. If you care about chemicals leaching into your lunch, get tempered glass containers (Pyrex, borosilicate, or similar) and don’t overthink it.

Plastic — even the ones stamped “microwave-safe” — can leach endocrine-disrupting chemicals when heated. That label only means the plastic won’t melt or warp. It says nothing about what ends up in your food. The hotter and greasier the food, the worse it gets. Reheating spaghetti in a plastic Tupperware is a gamble you don’t need to take.

Ceramic is also fine, as long as there’s no metallic trim or glaze you’re unsure about. Glass is just easier because it goes from fridge to microwave to table without drama. Stainless steel is great for carrying, but don’t microwave it. And those silicone lids? Most are heat-stable and generally considered safe, but glass is the boring, reliable choice.

One practical note: microwave without the plastic lid on. Use a paper towel or a glass plate to cover if you need to avoid splatter.

Your lunch deserves better than a container that degrades every time you heat it up.