Caffeine enters the bloodstream through the [[stomach]] and [[small intestine]] and can have its effects as soon as 15 minutes after it is consumed. Once in the body, caffeine will stay around for hours: it takes about 6 hours for one half of the caffeine to be eliminated. | Caffeine enters the bloodstream through the [[stomach]] and [[small intestine]] and can have its effects as soon as 15 minutes after it is consumed. Once in the body, caffeine will stay around for hours: it takes about 6 hours for one half of the caffeine to be eliminated. |