Can You Put Thermos in the Microwave? (Answered)

Categorized as Microwave
Can You Put Thermos in the Microwave

Listen up, folks! We all know and love this brand that keeps our beverages at the perfect temperature, whether we’re lounging in our humble abodes or gallivanting about. But hold onto your hats, because we’ve got a real head-scratcher for you today: is it safe to microwave a Thermos? This is a tricky one, and the answer isn’t so clear-cut. The web is rife with mixed messages, with some folks swearing up and down that it’s perfectly fine, while others vehemently declare it to be a hard pass. So, what’s the dealio?

Here’s the lowdown: some people are operating under the false assumption that a Thermos can take the heat of the microwave. In reality, most Thermoses are made of a fancy metal called stainless steel, which can be a real fire hazard when exposed to microwaves. Plus, the thick walls of a Thermos can cause uneven heating, which can lead to some parts of your drink being piping hot while other parts are stone-cold. Yikes!

So, can you put a Thermos in the microwave? In short, no. It’s not worth the risk of damaging your microwave or causing a fire. If you need to heat up your food or drink, it’s best to do so before transferring it to your Thermos.

Here’s everything else you need to know about heating up food and drinks in a Thermos.

How To Tell If A Container Is Microwave Safe

If you’re not sure whether your particular container is microwave safe, there’s an easy way to check. Just look for a symbol on the bottom of the container—if it has a microwave icon, that means it’s safe to use in the microwave.

If there’s no symbol, or if the container has a ‘do not microwave’ symbol, it’s best to err on the side of caution and transfer your food or drink to a different container before heating.

You can also visit the manufacturer’s website to check for specific product information. Under the ‘Care & Use’ section, you’ll be able to find out whether each product is microwave safe.

Lastly, even if your container has a microwave-safe symbol, you might still want to do a simple test before microwaving. Place the container in the microwave with a cup of water, and heat it on high for one minute. If the container gets hot, it’s not microwave-safe. But if the water gets hot and the container stays cool, it’s safe to use.

How to Preheat a Thermos

If you’re trying to keep your food or drink hot, it’s always best to preheat your Thermos before adding any contents. This will help to retain the heat and prevent your food from cooling down too quickly.

To preheat a Thermos, simply fill it with boiling water and let it sit for a few minutes. Then, empty the water and add your food or drink while it’s still hot. screw on the lid tightly to keep the heat in.

By doing this, you can be sure that your Thermos is nice and warm before adding anything to it. This will help to keep your food or drink hot for anywhere from 5 – 12 hours. To be sure, check the instructions that come with your particular Thermos to find out the exact amount of time it will keep things hot.

Your food and drink will only be safe to consume during this time frame. Don’t eat or drink anything from your Thermos if it’s been sitting for longer than the recommended time, as bacteria may have started to grow.

Safety Tips For Using a Thermos

Now that you know how to preheat a Thermos and how to tell if it’s microwave-safe, there are a few other things to keep in mind when using one.

Here are some safety tips to follow:

Once a Thermos is Opened, Any Leftovers Should be Discarded

Leftovers are a part of life. Whether it’s the extra food from a dinner party or the remnants of your lunch, leftovers can be tempting to save for later.

However, when it comes to leftovers that have been stored in a Thermos, it’s important to remember that once the Thermos has been opened, any leftovers should be discarded. The reason for this is that bacteria can quickly multiply once the Thermos has been opened, and this can lead to food poisoning.

If Your Thermos is Broken, Don’t Eat or Drink from It

If your Thermos has not kept your food or drink hot (or cold) for the recommended amount of time, it’s best to discard the contents and get a new one. Harmful bacteria can grow quickly in food or drink that has not been kept at the proper temperature, and this too can lead to food poisoning.

Similarly, if your Thermos is dropped or damaged in any way, it’s best to get a new one. A broken Thermos can be dangerous, and even if there are no visible signs of damage, the ability to keep food or drink hot (or cold) may be compromised. Make sure to test the Thermos before using it to make sure that it’s still safe.

Following these simple tips will help to ensure that you’re using your Thermos safely and effectively.

What Can You Put in a Thermos?

When most people think of a thermos, they think of something that you use to keep your coffee hot on a cold winter day. And while that is definitely one use for a thermos, it is not the only use. There are many things that you can put in a thermos that will keep you warm (or cool) all day long. Here are just a few ideas.

  1. Hot oatmeal – Start your day off right with a hot breakfast. Just make sure to leave room for milk and toppings!
  2. Congee – This Chinese rice porridge is perfect for a hearty lunch. Add some vegetables, meat, and seasonings to make it even more delicious.
  3. Latte or tea – A classic use for a thermos! Make sure to steep your tea for the appropriate amount of time so it doesn’t get too strong.
  4. Hot chocolate – A thermos full of hot chocolate is the perfect treat on a cold winter day. Add some marshmallows or whipped cream for an extra special treat.
  5. Soup or chowder – These hearty dishes are perfect for a winter lunch or dinner. Just make sure to add some crackers or bread on the side so you don’t get too full.
  6. Stew – Another great option for lunch or dinner, stew can be made with just about any combination of meats and vegetables you like. Serve it over some rice, noodles, or potatoes to soak up all the deliciousness!
  7. Chili – This classic comfort food is always a hit. Make a big batch and freeze individual portions so you can have them on hand whenever the craving strikes!


A thermos is a great way to keep your food or drink hot (or cold) for hours at a time. Just make sure to preheat it properly and discard any leftovers that have been stored in it.

Also, be sure to check it for damage before using it, as a broken thermos can be dangerous. When it comes to what to put in your thermos, the sky is the limit! Just make sure to leave room for liquid if you’re planning on storing soup or stew. And don’t forget the crackers or bread on the side. Enjoy!

By Rosie Elliott

I’m Rosie. I’m a professional chef with experience in Western, Mediterranean, and Italian cuisine. I’ve been cooking for over 15 years, and I have two daughters that keep me busy!