It is safe to drink coffee within 24 hours of being brewed. After 24 hours have passed, it is recommended the coffee be discarded.
Coffee can be reheated in the microwave, but this heating process can alter its taste. Coffee heated in the microwave may also taste burned or stale.
Coffee that has been brewed can be safely stored in the refrigerator for 3 to 4 days before it is discarded. Coffee should not be placed in the freezer.
If day-old coffee contains creamer or dairy products and was left out at room temperature, it should not be reheated. Dairy products that are not refrigerated for long periods of time should be thrown out.