how long before caffeine leaves your system
Advertisement. It only takes 45 minutes for 99% of the caffeine to be absorbed through these membranes. In humans the half-life for caffeine is anywhere from 4 to 6 hours on average, which explains why the average energy drink or coffeeâs effect lasts about 4 to 6 hours.his also interacts with the dopamine system in the brain, which is the feel good neurotransmitter. When adenosine is blocked by caffeine, the dopamine system works more efficiently. Furthermore, elevated levels of adenosine in the blood causes the adrenal glands to release adrenaline.