Most meal prep containers are microwave safe, but the material and temperature matter
Not every container that holds food is safe to heat in a microwave. The safest meal prep containers are made from glass, ceramic, or certain plastics labeled #2, #5. Containers made from polystyrene (#6) or unmarked plastic should not go in the microwave. Even if a container is microwave safe, the lid often is not—remove lids before heating, or check the label first.
The risk is real: unsafe containers can leach chemicals into your food when heated, and some materials warp or melt. A few minutes in the microwave can damage a container that seemed fine at room temperature. The good news is that most major meal prep brands now label their products clearly, and you can check the bottom of any container for a recycling number or microwave symbol.
Key Takeaways
- Glass and ceramic containers are always microwave safe; check the label on plastic containers for recycling numbers #2 (high-density polyethylene) or #5 (polypropylene).
- Plastic #6 (polystyrene) and #1 (polyethylene terephthalate) should not be microwaved because they can warp and release chemicals.
- Lids are often not microwave safe even when the container is, so remove them before heating unless the label says otherwise.
- If a container has no recycling number or microwave symbol, do not microwave it—transfer the food to a labeled safe container instead.
How to read the recycling number on your container
The recycling number is printed on the bottom of most plastic containers, usually inside a small triangle. This number tells you what type of plastic it is and whether heat will damage it. The safest numbers for microwaving are #2 and #5. These plastics have higher melting points and are less likely to leach chemicals when heated to typical microwave temperatures.
#1 plastic (polyethylene terephthalate, or PET) is common in takeout containers and some disposable meal prep boxes. It should not be microwaved. #6 (polystyrene) is the white foam used in some deli containers and takeout boxes—never microwave this. #3 (polyvinyl chloride, or PVC) and #7 (other) are also unsafe for microwaving. If you see any of these numbers, transfer your food to a #2, #5, glass, or ceramic container before heating.
Glass and ceramic containers: the safest choice
Glass containers have no chemical risk when microwaved because glass does not break down or leach anything into food, no matter how hot it gets. Borosilicate glass (the kind used in laboratory equipment and some premium meal prep containers) is even more durable and resists thermal shock—the sudden temperature change that can crack ordinary glass. Brands like Pyrex and Rubbermaid Brilliance make borosilicate glass meal prep sets with locking lids.
Ceramic containers are equally safe, though they can get very hot in the microwave. Always use an oven mitt when removing a ceramic container, and check that the glaze or paint on the rim is food-safe—some decorative glazes contain lead. Plain white or solid-colored ceramic is safer than painted designs. The downside of glass and ceramic is weight and breakage risk if you carry meals in a bag, but for home storage and reheating, they are the most durable long-term choice.
Plastic #2 and #5: microwave safe but with limits
Plastic #2 (high-density polyethylene, or HDPE) is used in some rigid meal prep containers and milk jugs. It can handle microwave heat but should not be used for very hot foods or long heating times. Most meal prep containers labeled #2 are safe for 1 to 3 minutes of microwave heating at standard power. If you need to heat food longer, transfer it to glass or ceramic.
Plastic #5 (polypropylene, or PP) is the most common material in microwave-safe meal prep containers sold by brands like Rubbermaid, Sistema, and Prep Naturals. It has a higher melting point than #2 and can handle moderate microwave use. However, repeated heating and cooling can degrade the plastic over time, so containers may become cloudy or brittle after a year or two of regular use. Even #5 plastic should not be used for foods that are extremely hot or oily, as the heat and oil can cause leaching.
Why lids are usually not microwave safe
Most meal prep container lids are made from a different plastic than the base—often #6 (polystyrene) or a rubber-like material that cannot withstand microwave heat. Even if the container itself is #5, the lid may not be. Lids can warp, melt, or release chemicals when microwaved. The safest practice is to always remove the lid before heating, even if you are only reheating for 30 seconds.
Some premium brands now make lids from #5 plastic that can handle brief microwave heating. Check the label on the lid itself—it will say "microwave safe" or show a microwave symbol if it is safe. If there is no label, assume the lid is not safe and remove it. You can always put the lid back on after the food has cooled slightly.
What happens when you microwave an unsafe container
When plastic #1, #3, #6, or #7 is heated, it can warp, crack, or release chemicals like BPA (bisphenol A) and phthalates into your food. These chemicals are endocrine disruptors, meaning they can interfere with hormone function. The risk is higher with fatty or oily foods, which absorb chemicals more readily than water-based foods. A single use is unlikely to cause harm, but repeated exposure over months or years can add up.
Polystyrene (#6) is particularly problematic because it breaks down easily under heat and can release styrene, a chemical linked to nervous system effects. Even if the container does not visibly melt, the damage may be happening at a molecular level. The safest approach is to avoid microwaving any plastic container unless you can confirm it is #2 or #5 and the label explicitly says it is microwave safe.
Alternatives if your container is not microwave safe
If your meal prep container is not labeled microwave safe, you have three options. The first is to transfer the food to a glass or ceramic bowl before heating. This takes an extra 30 seconds but eliminates any risk. The second is to reheat on the stovetop in a pot or skillet—this actually heats food more evenly than a microwave and works well for soups, grains, and proteins. The third is to eat the meal cold or at room temperature, which is fine for salads, grain bowls, and some prepared dishes.
If you meal prep regularly, investing in a set of glass or #5 plastic containers with microwave-safe lids will save you time and worry. Glass containers cost more upfront but last for years, while #5 plastic containers are cheaper but may need replacing after a year or two of regular use. Either way, you will know for certain that your container is safe every time you reheat.
Frequently Asked Questions
Can I microwave a container if it does not have a recycling number?
No. If there is no recycling number or microwave symbol on the bottom, you cannot be sure what the plastic is made of. Transfer the food to a labeled safe container instead. Many older or cheap containers do not have labels, and guessing is not worth the risk.
Is it safe to microwave plastic #5 with hot sauce or oil?
Not for long periods. Fatty and acidic foods cause plastic to break down faster and leach chemicals more readily. Heat the food for the shortest time possible, and if the meal is very oily or spicy, use glass or ceramic instead.
What if my container melted a little in the microwave?
Throw it away. If the plastic has warped or melted, it has already released chemicals into the food and the container is no longer safe. Do not reuse it. This is a sign the container was not microwave safe to begin with.
Are stainless steel meal prep containers microwave safe?
No. Metal reflects microwave energy and can cause arcing (sparks) inside the microwave, which can damage the appliance or start a fire. Transfer food from stainless steel containers to glass or ceramic before heating.
Do I need to remove the lid even if it says microwave safe?
Not if the label says the lid is microwave safe. However, be careful—the lid will get hot, and steam can build up under a closed lid and cause burns. Leave the lid slightly ajar or remove it partway to let steam escape.