Can You Drink Leftover Coffee the Next Day?

Every one of us must have experience with a day-old coffee from the murky container of stuff that's been made in the morning only to be left alone all day or night. Anyone who has tried this probably agrees with the statement that this is not the best coffee around.

Common sense says that a brewed coffee can't stay good forever, but when does our coffee go bad, and why?

Then there's something else. Since most of the regular coffee pots are very big for only one person to drink every morning alone, there is yet another question: Can you drink leftover coffee the next day?

It turns out that there is not a single answer to these questions as it depends on a variety of factors including how old the coffee is as well as what was added to it. Keep on reading to find out more.

Can You Drink Leftover Coffee The Next Day - What You Need To Know

To answer this question briefly and simply; yes, it is fine for us to drink leftover coffee. The general consensus regarding coffee is that it is good for our health - and in some fortunate cases, the more we drink, the better it is for us.

Yet when does the freshly brewed cup function as a source of coffee's magical antioxidant powers, and when does the eight-hour-old pot come into play?

Here are some factors worth considering.

Unrefrigerated Milk in Coffee

Let's say I've already added milk and then left my coffee out on a counter. What does it mean? Well, nothing too great - because drinking milk that has been sitting there unrefrigerated for more than 2 hours is not a very good idea even if you mix it with coffee.

How Old Is The Pot Of Coffee?

As a rule of thumb, there exist two distinct milestones in a lifetime of the pot of coffee. The first one usually occurs at around thirty minutes after brewing when our coffee cools as well as loses flavor. And the next comes after four hours when all the oils lose their original characteristics and go bad, after which our coffee becomes more acidic.

Some people may think that heating up their coffee in a microwave can be helpful but unfortunately, it is never effective as it won't be able to reverse all the deterioration in taste. However, drinking hours-old coffee can't possibly be dangerous, even if by doing so we will be making some highly professional baristas shudder.

Access To The Microwave

If there is not any other choice left but to recycle our cup of coffee with milk, it's wise to minimize the safety concerns by microwaving it as this is good at killing some of the bacteria.

Additionally, keep in mind that coffee keeps oxidizing even after brewing which means that unless we store it in the thermos, it'll only remain in its best quality for 30 minutes or so. As for the freshness of the coffee, it depends on the beans we use which means that if we use stale grounds, they will certainly produce a stale cup of coffee.

The Chemistry Of Coffee Oxidization - What's Going On

cold coffee with beans on the side

Contact with air causes the oxidation of roasted coffee beans. Essentially, this is exactly the same thing which happens to apples when we slice them open, leaving them for a while.

Although oxidation of coffee beans isn't visible to a plain eye, it still has a highly significant impact on their taste as oxidation causes the deterioration of the flavor compounds existing in the coffee which then get released into the air upon contact.

As for the process of brewing coffee, it is actually oxidization. So when those coffee beans finally come into contact with water, they start releasing their aromatics, acids as well as oils into the water.

And this chemical reaction is exactly what produces that flavorful cup of coffee we all enjoy and love.


When we leave our coffee sitting alone all by itself for too long, the reaction between oxygen and hydrogen will raise the pH level of a coffee, making it taste "stale" or bitter. That's why if we cannot drink it all right away, we should place it in a good container such as a thermos bottle.

Over-extraction can also be another common cause of bitterness. To avoid it, the grind size shouldn't be too small. Also, you shouldn't brew the coffee for too long. By keeping these two very important tips in mind, you can guarantee that next time you’re about to make a coffee, it'll be living up to its highest quality.

Stale Grounds Make For Stale Coffee

Coffee is like any other food stuff that can't possibly last forever.

Usually, the older our coffee grounds are, the more they've been subject to oxidation. And coffee that is made from old grounds will always taste stale or bitter even immediately after brewing.

However, coffee doesn’t go bad in the same way as milk does, for example. Rather than omitting any rotten smell, it is characterised by an absence of scent.

So even though stale coffee isn't dangerous for us to drink, it'll still be very unpleasant.

Can You Drink Leftover Coffee the Next Day: The Verdict

All in all, the answer to a question of the coffee's lifespan usually depends on where our priorities lie. For example, if we've decided to merely seek a caffeine injection, 1 hours-old coffee will still be able to do the trick for us.

With that said, don't wait for any more than a day or even over 2 hours when there's an unrefrigerated dairy product involved.

For coffee snobs who only enjoy drinking the finest of the brews, unfortunately, the options may be more limited as it's better to brew a fresh pot and then drink it within the first half hour.