Note on Caffeine: People react differently to it. Some it has minimal effect, other strong & slow. It on the top 10 list of allergies.

Caffeine takes 4-7 hours to get "into the blood stream" and be effective. The takes 7-11 hours to be removed. It's usually the sugar & amendments to the coffee that wake a person up the first hours.

That means that for some, that morning coffee is the reason they can't sleep at night.

Also watch out as some medicines add caffeine to heighten the body's response to the drug.