Can you microwave plastic containers?

A microwave-safe mark means the maker has tested the container against the FDA food-contact rules at the temperatures microwaving produces, and that any substances migrating into food stay within the limits FDA set. Plastics made for cold storage — margarine tubs, deli pots, yogurt cups, single-use water bottles — were never tested for that and can warp or leach when heated. Fatty foods are the hard case, because oil exceeds 100 °C while water cannot, so the plastic sees a higher temperature than the food overall. Replace microwave-safe containers once they craze, cloud or warp, because those are signs the polymer has degraded.

How to do it properly

1. Check the base for the microwave-safe wording or the wavy-lines symbol
2. Vent the lid or leave it ajar so pressure cannot build
3. Use short bursts and stir, rather than one long run at full power
4. Retire any container that has gone cloudy, crazed or warped

What goes wrong

• Untested plastics can exceed FDA migration limits when heated
• Sealed lids build pressure and pop, spraying hot food
• Greasy foods create hot spots well above 100 °C that deform the tub

Other options

• Decant into glass or ceramic, which have no heat limit at these temperatures
• Use a microwave-safe silicone or borosilicate glass container

Other "can you microwave" questions

• Can you microwave styrofoam? It depends — Only if the container is labeled microwave-safe, and most takeout foam is not.
• Can you microwave aluminum foil? No — No — foil reflects microwaves and the edges arc, which can start a fire.
• Can you microwave eggs? It depends — Beaten or pricked eggs, yes. A whole egg in its shell will explode.
• Can you microwave Tupperware? It depends — Yes, if that specific piece carries the microwave-safe symbol on its base.
• Can you microwave paper plates? It depends — Plain white paper plates are fine; anything with metallic trim or a foam layer is not.
• Can you microwave metal? No — No — metal reflects microwaves, arcs at edges, and can damage the oven or start a fire.
• Can you microwave breast milk? No — No — microwaves create hot spots that scald a baby even when the bottle feels cool.
• Can you microwave takeout containers? It depends — Only if the container is marked microwave-safe — most are not, and metal-handled ones never are.
• Can you microwave cardboard? It depends — Plain dry cardboard is usually fine briefly; anything with glue, staples, wax or foil is not.
• Can you microwave glass? It depends — Yes for ordinary heatproof glass; no for leaded crystal, and never straight from the freezer.
• Can you microwave water? It depends — Yes, but very clean water can superheat and erupt when you move the cup.
• Can you microwave ceramic? It depends — Yes for plain glazed ceramic; no if it has metallic trim or is unglazed and porous.