The average circulating time of caffeine in a healthy adult is 3.5 hours. This figure is influenced by multiple factors including the subject's body weight, race, sex, and age. In fact, the stimulant effect of caffeine is increased by its longer stay in the bloodstream by:
- alcohol intake
- use of oral contraceptives
- being male (men keep caffeine in their bloodstream longer than women)
- being Asian (Asian populations metabolize caffeine much more slowly
than Caucasians)
Article published on
English
Italian 
German 
Spanish