how long does it take caffeine to work
How long does it take for caffeine to be eliminated from the body? 3. 12-16 hours: Caffeine has a half-life of about 6 hours, meaning half of the caffeine will be left in your system 6 hours after ingestion, and half of whats left 6 hours later so on and so forth.Most of the caffeine will be gone after about 16 hours.Good luck! ...Read more.. Caffeine: If you are referring to Intravenously administered caffeine, I'd say within a few seconds of administration. If you are referring to orally ingested caffeine in the form of coffee, chocolate, soda or any other caffeine containing beverage, I'd say within 15 minutes, give or take a few minutes.