Caffeine is a naturally occurring drug that is found in leaves and seeds of many plants including coffee beans and tea leaves.
Caffeine is also made artificially and added to some foods and drinks.
Caffeine is a drug because it stimulates the central nervous system, causing increased alertness.
Although caffeine does not cause the severity of withdrawal or harmful drug-seeking behaviors as street drugs or alcohol.
For this reason, experts do not consider caffeine dependence an addiction.
When taken by mouth: Caffeine is likely safe for most healthy adults when used in doses up to 400 mg daily.
This is equal to about 4 cups of coffee.
Caffeine is possibly unsafe when used for a long time or in doses over 400 mg daily.
Caffeine is a naturally occurring central nervous system (CNS) stimulant of the methylxanthine class and is the most widely taken psychoactive stimulant globally.
Up to 400 milligrams (mg) of caffeine a day appears to be safe for most healthy adults.
That's roughly the amount of caffeine in four cups of brewed coffee, 10 cans of cola or two "energy shot" drinks.
Keep in mind that the actual caffeine content in beverages varies widely, especially among energy drinks.