Can You Microwave Coffee?

Coffee is one of the favorite beverages across the world.

Most of today’s modern cultures have some type of coffee they like to enjoy.

It’s also a great way to wake up or get a midday pick-me-up; however, there is one common problem everywhere – cold coffee.

You may be tempted to microwave coffee (which you can do), but be aware of a few key points before you make that decision.

What Happens to Coffee When You Microwave It?

Coffee can indeed be heated in a microwave, but it’s essential to know that it will change its flavor dramatically.

Coffee is an experience that involves both the sense of taste and smell. A microwave destroys the aroma of the coffee and thus, changes its flavor.

Instead of the complex smell and taste you love, your coffee becomes flat and bitter-tasting when it’s reheated in the microwave.

If you love coffee or you feel you must have it, and there’s no other way to reheat it, then you may want to consider using the microwave.

You need to know a few things first to get the best possible outcome.

The Bitterness Factor

Anytime you reheat your coffee, especially when you microwave it, you encourage quinic acid, which causes a bitter flavor, to increase and intensify the bitterness of the coffee.

There is also caffeine acid that also serves the same purpose.

Heating coffee in the microwave intensifies the bitterness and kills the balance of other flavors that make coffee so appealing.

This problem is also more pronounced in coffee preparations with bits of ground or sediment in the bottom.

This unappealing effect occurs significantly in percolated coffee, French press brews, and Turkish coffee.

The bits of ground continue to brew, especially when the coffee is microwaved, and tips the balance of delicate flavors.

You’re essentially overcooking or over brewing the coffee, and much like regular food, the flavor becomes unappealing.

This occurrence is especially problematic for people using the warming feature on their automatic coffee pots throughout the day.

It helps to brew small batches if possible and make more as needed to avoid an unpleasant taste for a better flavor.

How to Reduce the Bitterness When Microwaving Coffee

The method for reheating coffee in the microwave to avoid increasing the bitter flavor is pretty simple.

You can put the microwave on 80% power or level 8 instead of 10. This process allows your coffee to heat slower and brews less quickly, thus reducing the unpleasant effect the microwave produces.

If you plan to microwave your cup of coffee, you should only put it in there for approximately 45 seconds, but no longer than one minute.

Otherwise, it will begin to turn too bitter to drink rapidly, and it might become dangerously hot.

One way to combat that unpleasant bitterness is to add more fresh cream or sugar to the original mixture.

If you drink it black, there’s probably not much else you can do. A dab of sweetener may help cut the bitterness, however.

Risks to Be Aware of Before Reheating

In some instances, coffee can pose a health hazard depending on the age of the coffee and the ingredients.

Coffee mixed with dairy products may pose a risk if they’ve been sitting around for an extended period of time.

If the coffee is more than an hour or so old, you probably want to throw it out to avoid potential illness.

Coffee has particular time markers to familiarize yourself with to ensure you get a good cup of coffee without it going bad.

First, know that coffee can begin to lose its original flavor after about 30 minutes.

In four hours, that same cup of coffee begins to go bad because the oils in the coffee go bad.

Don’t drink coffee in any of the following situations:

  • You’re unsure how old the coffee is. If it’s sitting in an office and likely brewed early in the day and it’s later in the afternoon, avoid it.
  • It has dairy creamer and has been sitting for a few hours. The milk turns bad and can make you ill.
  • It’s reheated more than once. The flavor is unbearable for most coffee drinkers.
  • It’s left warming on the burner for a long time.
  • It’s over four hours old.

The old saying, “When in doubt, throw it out,” applies in this instance.


Don’t use styrofoam or paper cups to microwave your coffee. They can catch on fire or melt. Instead, use a microwave-safe mug.

You’ll know if it is microwave safe because it’s stamped on the bottom.

Don’t use handmade mugs or pottery in the microwave.

The glaze or paint can get into the coffee and cause health issues. Don’t use glass or metal because it can break or cause a fire.

Always be careful when removing coffee from the microwave.

It can be scorching and might cause burns if you spill it.

Additionally, the mug may be hot to the touch and can burn you.

You don’t want to reach for a hot cup and then drop it because it’s hot. You may even spill hot coffee on yourself.

Alternatives to Using a Microwave to Reheat Your Coffee

There are other ways to reheat your coffee that give better results. ‘

The best method is to heat slowly in a pan on the stove.

This method keeps the brewing process from speeding up and can help prevent it from becoming extremely bitter.

It helps to stir it during heating to help avoid the bottom from brewing too quickly or burning.

You may also want to try to pour the coffee in the coffee pot if it’s empty and turn on the warming feature for a few minutes if there isn’t a stove handy.

It will warm the coffee slowly and allow you to heat it without burning it.

It would be best to stir it or swish it around once or twice to prevent the bottom from burning or turning bitter.

Preventing Cold Coffee

The most effective way to keep your coffee warm is by using an insulated thermos or coffee mug.

Instead of keeping the old trusty coffee cup in your hand, you should try to use an insulated cup or thermos if you find yourself having cold coffee issues daily.

If you refuse to give up your coffee cup, an easy way to prevent it from getting cold too quickly is to put a lid or place something over the top of the coffee cup.

It won’t keep your cup as warm as an insulated version, but it can help slow the process to give you more time to enjoy it.

Some FAQs

Q: So, does reheating the coffee reduce the caffeine level in the coffee?

A: No, the caffeine levels stay the same regardless of how hot or cold the coffee gets or if you reheat it in the microwave or on the stove.

So, this is why so many people are willing to reheat the coffee if there isn’t any more available.

What is the best way to reheat coffee to avoid bitterness?

A: If you have a stove or a warmer, you probably want to try this method to avoid choking down an unpleasant cup of coffee.

This is for when you absolutely need your caffeine to make it through the day.

How old is too old to drink?

A: If the coffee is over four hours old, you want to toss it.

The oils in the coffee begin to go bad around 3 or 4 hours, and it may make you ill or be terrible to drink. If you have dairy, you don’t want to drink it if it’s over an hour old.

After a couple of hours, dairy goes bad in coffee and can make you ill.

What is the best way to keep coffee warm to avoid reheating?

A: The best way to keep coffee warm is to keep it in a thermos or insulated mug designed to keep drinks hot.

If you bring a thermos, you can pour a hot cup of coffee multiple times per day and reduce the bitter flavors.

However, an insulated mug is more accessible to drink from and usually has a lid that closes or has a spout for a straw.


Ultimately, if you drink coffee solely for the flavor you probably already know (or guessed) you shouldn’t reheat it.

No matter how you reheat coffee, it changes the flavor, intensifies the bitter flavor, and throws off the balance of sweet, salty, bitter, and aromatic.

However, if you’re going to reheat it, the worst method is the microwave. This type of reheating will damage the flavor significantly and make it unpleasant to drink.

Most people who regularly reheat coffee aren’t drinking it for the taste but rather for the caffeine.

Enjoying your favorite cup of coffee is something to look forward to every day, however knowing these facts and using the suggestions can make keeping coffee warmer, longer, easier and safer.

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