Is it Okay to Drink Day Old Coffee?

There’s no doubt that coffee is one of the most popular and widely consumed drinks all around the world. People just love the comforting boost of energy that this beverage can provide.

One of the worst feelings in the world is walking over to the coffee station in your office only to discover that new coffee hasn’t been brewed for hours. However, when you’re facing this difficult situation, you might find yourself wondering, “Is it OK to drink day-old coffee?” 

Old coffee often has an off putting bitter flavor that leads most people to try and avoid it. However, does this mean it’s really bad for you? Does coffee really ever go bad? Why does allowing it to sit change the flavor? Here’s what you need to know about day-old coffee and whether or not it’s safe for you to drink when you find yourself facing the bottom of the pot.  

How Long Does Coffee Stay at its Best? 

In reality, if you’re looking to enjoy the best, most delicious cup of coffee, then all the experts say that you really need to drink it within 30 minutes of it being brewed. Freshly brewed coffee has a bite and complexity of flavors that fade the longer it sits out. Believe it or not, what causes this massive change in flavor is actually the air itself. 

When coffee beans are roasted, there is a reaction between the natural sugars and amino acids that ends up creating an array of new compounds within the beans themselves. This is what creates that wonderful, full flavor and smell that so many people enjoy.

The only problem is that these compounds are exceptionally sensitive. The very moment they are exposed to the oxygen in the air they’ll start oxidizing and will essentially decay. This has a tremendous impact on the overall flavor of the coffee inside your cup and the longer your coffee sits, the more it’s going to oxidize and the worse it’s going to taste. 

Frankly, those of us who are parents who survive on coffee may be too tired overall to tell the difference in taste, especially after the same cup of coffee has been microwaved and forgotten numerous times in a morning.

Coffee and its Antibacterial Qualities 

Having to throw away that full cup of coffee just because it’s been sitting for a while can be one of the most frustrating feelings. Because of this, many people find themselves taking advantage of the last cup in the pot and just adding a bit of extra sugar or creamer to mask the poor taste. However, could this actually be bad for you? 

Well, there are a number of different factors you’ll need to take into consideration. First, you need to consider the fact that coffee comes with a range of natural antibacterial qualities mainly due to its high level of acidity. This means that your coffee will be able to fight off some germs all on its own. 

Also, you need to consider how your coffee has been stored. Think about whether or not the coffee has been left sitting without any source of heat or if the coffee was placed inside the fridge after it was brewed. The storage method you use for your cup of coffee can help lengthen the amount of time that your coffee is able to remain “safe.”

Refrigerators can be extremely helpful in this regard, both limiting the amount of oxygen the coffee is exposed to, as well as keeping it at the perfect temperature to ensure freshness. 

Growth of Mold and Bacteria in Coffee

Even though coffee does have its own natural antibacterial qualities, that doesn’t mean that it will be able to fight off all the germs and bacteria that come its way. In fact, Assistant Professor at Saint Louis University, Donna Duberg, made it a point that coffee only has the ability to fight about 50% of the bacteria it comes into contact with.

This means that every time you take a swig of that day-old coffee, you could be putting yourself at risk for some really uncomfortable consequences.  

According to Duberg, “Germs are present in every corner of our lives …. Are there germs in our coffee makers? Yes.” Germs and bacteria are a serious concern that you’ll always need to keep in the back of your mind. While your coffee may be perfectly fine after it has been sitting out all day, whether or not it’s worth the risk of you getting sick is up to you. 

What Happens To Coffee When You Add Milk? 

Another incredibly important factor that you absolutely must take into consideration will be the preparation of your coffee. Has your cup been left black or did you add milk and sugar when it was first brewed? Believe it or not, this can actually play a much larger role in how long it’s safe for you to drink than even the coffee itself. 

According to the United States Food and Drug Administration, refrigerated food items such as milk and other dairy products should never be out of refrigerator temperatures for longer than two hours. This is because these particular products are especially sensitive to mold and bacteria growth, and leaving them sitting out will put them at serious risk of contamination. 

This means that even if you add milk to your coffee, the risk remains the same. Drinking coffee with milk after the two-hour period can result in you ending up seriously ill. If you drink your coffee with milk, make sure you either stick it in the fridge as soon as you can or simply add the milk later on when you actually have time to sit down and enjoy your cup. 

It doesn’t take a rocket scientist to recognize when liquid dairy products have turned for the worse. You probably won’t get the cup to your lips before your nose would alert you to the bad situation in your coffee cup.


Asking yourself, “Is it OK to drink day-old coffee?” really does depend on a variety of factors. However, while your old coffee certainly isn’t the worst thing you can drink throughout the day, trying to enjoy a freshly brewed cup as often as you can will always be the best way to go.