Yes, you can reheat coffee. It is safe as long as the coffee has not been sitting out too long, but it will taste flatter and more bitter than a fresh cup. Reheating cannot bring back the aromas that escaped as it cooled, and holding coffee hot makes it harsher. If you do reheat, the microwave is the best way: heat it in short bursts, stir, and stop as soon as it is hot, without letting it boil. Black coffee left out for a few hours is fine to reheat; coffee with milk should not sit out for more than 2 hours.
Why Reheated Coffee Tastes Worse
- Aroma is lost. Much of what we taste in coffee is aroma, and those compounds evaporate as the coffee sits and again as it is reheated. That is why reheated coffee tastes flat.
- It turns more bitter and sour. Over time, especially while coffee is kept hot, chlorogenic acids break down into compounds such as quinic acid that taste harsher and more astringent. The longer coffee sits, the more noticeable this is.
- Overheating makes it worse. Boiling or scorching the coffee drives off even more aroma and adds a burnt edge.
Delicate light roasts with fruity or floral notes suffer most. Dark roasts and everyday blends hold up better because their roasty, chocolatey flavors are more robust. Caffeine is not affected by reheating, so a reheated cup is just as strong.
How to Reheat Coffee
| Method | How | Verdict |
|---|---|---|
| Microwave | 20 to 30 seconds at a time in a microwave-safe mug, stirring between bursts | Best for a single cup: fast and easy to control |
| Stovetop | Small saucepan over low heat, stirring, removed just before it simmers | Good for several cups; watch it closely |
| Warming plate or hot plate | Coffee kept hot in the pot for a long time | Avoid: it slowly cooks the coffee and makes it bitter |
| Kettle or boiling | Bringing coffee to a boil | Avoid: drives off aroma and tastes burnt |
- Use a microwave-safe mug, not a travel mug with metal parts.
- Heat in short bursts of 20 to 30 seconds and stir between each. Stirring evens out hot spots and helps prevent coffee from superheating and bubbling over.
- Stop when it is hot, not boiling. Coffee tastes best around 140 to 160°F (60 to 70°C). If it steams but is not bubbling, it is ready.
- Reheat only what you will drink now. Reheating the same coffee more than once makes it worse each time.
Coffee with milk reheats the same way, but heat it gently and stir well; milk can scorch and form a skin if it gets too hot. A splash of fresh hot milk or fresh coffee can also bring a lukewarm cup back up to temperature without reheating it at all.
Is It Safe to Reheat Coffee?
For black coffee, yes. Plain coffee is not a good home for bacteria, so a cup or pot left out for a few hours is safe to reheat, even though it will taste stale. Coffee with milk or cream is different: like any dairy, it should not sit at room temperature for more than 2 hours. Reheating does not fix milk that has been left out too long.
| Coffee | Room temperature | Fridge (sealed container) |
|---|---|---|
| Black coffee | Safe for several hours; tastes stale after about 30 minutes | About 3 to 4 days |
| Coffee with milk or cream | No more than 2 hours | About a day |
| Cold brew | Keep it refrigerated | About 1 week |
Throw out any coffee that smells sour or off, or shows signs of mold.
Can You Reheat Coffee the Next Day?
Yes, if it is black coffee that you put in the fridge in a covered container. It is safe to reheat for the next few days, though it will taste noticeably flatter than fresh. Black coffee left out on the counter overnight is usually still safe if it looks and smells normal, but it will taste stale, and anything with milk left out overnight should be thrown away. Day-old coffee is often better used cold, as iced coffee, than reheated.
Better Alternatives to Reheating
- Keep it hot in the first place. A thermal carafe or an insulated, lidded mug keeps coffee hot for hours without the cooked taste of a warming plate. Preheating your mug with hot water also helps.
- Brew less. Make one cup at a time with a pour-over dripper, a French press or an AeroPress, so there is nothing left to go cold.
- Turn leftovers into iced coffee. Chill extra coffee in the fridge and pour it over ice with milk. Cold coffee tastes smoother and less bitter than reheated coffee.
- Freeze coffee ice cubes. They chill iced coffee without watering it down.
- Cook with it. Leftover coffee adds depth to chocolate desserts, tiramisu, chili and meat rubs.
- Make cold brew. If you like to sip slowly, cold brew is meant to be drunk cold and keeps for about a week.
If reheated coffee always tastes harsh to you, the problem may start with the brew itself. Our guide to why coffee tastes bitter or sour walks through the fixes, and our guide to brewing methods helps you find a better way to make just one cup. The same rules apply to espresso; see how long an espresso shot lasts.
Former roastery owner and coffee tour operator. Steve spent five years roasting coffee for his own shop and wholesale customers. More about Steve