Is It OK To Drink Day Old Coffee? 3 Important Facts

What happens if you leave your cup of coffee out until the next morning? Is it OK to drink day old coffee? Why or why not? Let’s find out the reason why.

Is It OK To Drink Day Old Coffee - holding a cup of coffee beside a laptop
Drinking day old coffee tastes unpleasant

Picture this scene: a pot of coffee sits on a breakroom or gas station counter, perhaps with the light still on the machine. You pick up the pot and notice that it’s warm but not hot. Since you’re so exhausted, you decide to pour a cup. After raising it to your lips, you notice the coffee is bitter and unpleasant. Congratulations, you just drank day-old coffee. 

Most of us have been in this situation before and wondered, is it OK to drink day-old coffee? Technically speaking, yes, it is. However, there is some dispute about the definition of “OK.”

Can you drink day-old coffee? You can drink it but it may taste rancid and bitter. Day-old coffee won’t teeming with harmful bacteria like some other beverages, but its taste doesn’t compare to a fresh pot. However, if you added creamer or milk then it’s probably not safe to drink.

So, with that in mind, let’s take a closer look at what happens with coffee when it sits out and what you can do about it. 

The Science Of Coffee Oxidation

All foods oxidize as they sit out in the open. Oxidation is part of what causes food to rot (along with bacteria). Some products, like coffee, take a long time to oxidize to the point where you’ll get sick from ingesting them.

However, oxidation not only makes coffee expire; it also changes its flavor profile. It’s important to note that oxidation also happens during the roasting and brewing process. The longer the beans are heated, the more they oxidize.

Over time, the natural compounds in coffee will break down, leading to a more acidic and bitter-tasting beverage. So, day-old coffee will experience much more oxidation than a fresh batch.

One way to mitigate this process is to store the liquid in the refrigerator, exposing it to less oxygen and other environmental elements. That said, if you try to reheat cold coffee, you’ll degrade it much faster, leading to an even worse-tasting brew. 

Does Coffee Need To Be Refrigerated Once Brewed? 

Open refrigerator with lots of food and drinks
Don’t put your coffee inside a refrigerator immediately after brewing

Technically, no. Old coffee beans are safe to drink. While bacteria and mold can grow in brewed coffee, it takes a few days before they reach harmful levels. For example, if you leave a pot sitting in a coffee maker for a week, you’ll notice spots of mold growing on the surface. 

Coffee can be left out for several hours or a couple of days, provided it hasn’t been mixed with anything. Once you add other ingredients like milk and sugar, those elements will break down and grow harmful bacteria much faster. 

The Best Ways To Drink Day Old Coffee

Ideally, you won’t have to drink day-old coffee too often, but if you find yourself in this position, there are a few ways to mitigate any sour flavors or bitterness. 

  • Refrigerate the coffee ASAP – The sooner you can cool the liquid, the less it will oxidize, preserving the original flavor. 
  • Pour over ice – As we mentioned, reheating coffee degrades it further, making it extra bitter and unpleasant. So, it’s better to go the opposite direction and drink it cold. 
  • Mix with other ingredients – Once you pour the coffee over ice, adding cream and sugar can make it tastier and hide the harshness of the day-old brew. 

While it may be tempting to re-heat your coffee in the microwave, doing so will only oxidate the beverage faster, leading to a more bitter and burnt taste. If you’re going to microwave coffee, it should be relatively fresh (within a couple of hours if possible). 

The Final Word: Is It OK To Drink Day Old Coffee?

Drinking day-old coffee should be a last resort (unless you’re talking about cold brew varieties). Just because you can drink it and not get sick doesn’t mean you should. There are other ways to fix your caffeine, so don’t assume it’s day-old coffee or nothing. 

Individuals who like their coffee more acidic and bitter may not mind a day-old beverage. Older generations would often brew a whole pot at the beginning of the week and drink from it for a few days before replenishing it with new coffee. However, if you don’t have time to brew fresh coffee in the morning, prepare and store cold brew coffee beforehand. 

FAQs About Is It Ok to Drink Day Old Coffee

Does coffee go bad overnight?

If by “going bad” you mean that drinking will be harmful, no, it doesn’t. If coffee sits out overnight, it will be much more bitter in the morning than if you refrigerated it, but it won’t make you sick. 

Does all coffee taste bitter after sitting out?

Yes, all coffee will become more bitter after sitting out for a while. The difference might be less noticeable since lighter roasts are already relatively bitter than day-old dark roast coffee.


  • Jonathan

    Jonathan is an avid coffee drinker, although he's known to knock back a few energy drinks too. He's been a writer for over seven years, which is why caffeine runs through his veins. Find Jonathan on WriterAccess.