In today’s fast-paced culture, it’s common to see people sipping coffee throughout the day, often from the same cup they purchased hours ago. But what happens when that half-finished coffee sits out overnight? Is it still safe to consume the next morning?

Room-Temperature Coffee: A Health Concern
According to food safety guidelines, particularly from the U.S. Food and Drug Administration (FDA), beverages containing milk, cream, sugar, or flavored syrups should not be consumed after being left at room temperature for more than two hours. Such conditions create an ideal environment for bacterial growth, especially in milk-based drinks like lattes and frappés.
Even black coffee, which may seem safer due to the absence of dairy, poses its own concerns. Once brewed, coffee begins to oxidize. Over time, this process degrades beneficial antioxidants, alters the chemical profile of the drink, and can increase acidity, potentially leading to digestive discomfort.
The Risk of Contamination from Containers
The container in which coffee is stored also plays a role. Most takeout coffee cups are not designed to maintain internal temperature or prevent contamination. As the coffee cools, it may become susceptible to bacterial exposure. Adding straws can further introduce mouth bacteria into the beverage, compounding the risk.
Reheating Doesn’t Restore Safety or Quality
While reheating coffee might seem practical, it does not eliminate all bacterial risks. Furthermore, reheating may intensify bitterness due to prior chemical changes, resulting in an unpleasant taste and potential gastrointestinal discomfort.

Who Should Be Especially Careful?
Extra caution is advised for individuals who are pregnant, elderly, immunocompromised, or children. Even slightly spoiled beverages can cause serious health effects for these populations, including dehydration or foodborne illness.
Best Practices for Coffee Consumption
To ensure safety and quality, health experts recommend the following:
- Consume coffee soon after it is prepared.
- Refrigerate any leftover coffee within two hours.
- Discard dairy- or sugar-containing coffee after 24 hours.
- Use insulated, sealed tumblers when transporting coffee to maintain safe temperatures.
Ultimately, no matter how tempting that day-old cup might look, it’s best to prioritize freshness. For taste and health, a freshly brewed cup is always the safer and more enjoyable choice.
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