Caffeine is a tool to help you awake, perk up, concentrate, and help get through the day. Reduces tiredness, increases alertness and gives you a boost of energy. If you're not careful it can cause insomnia, headaches, dehydration, and high blood pressure. Caffeine considers a food additive and a drug, it passes into your bloodstream from your stomach and small intestine. It also causes the release of acid in the stomach, and you might have heartburn or indigestion after consuming caffeine. Medical professionals consider moderate consumption to be 200 to 300 milligrams(mg) of caffeine per day. You notice the effects of caffeine within 15 minutes. About 6 hours after you consume caffeine, half of it is still in your body. Caffeine may not completely clear your bloodstream until after 10 hours.