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The time it takes for the body to eliminate one half of a caffeine dose is normally between 3 to 12 hours. It is called the half-life of caffeine. Several factors can shorten or lengthen the half life of caffeine. Smoking, medications and diseases are some factors.
Caffeine begins to affect your body very quickly. It reaches a peak level in your blood within 30 to 60 minutes. It has a half-life of 3 to 5 hours. The half-life is the time it takes for your body to eliminate half of the drug. The remaining caffeine can stay in your body for a long time. Coffee accounts for 54% of the caffeine consumption in the world. Tea accounts for another 43%. On any given day, about 85% of Americans use caffeine products.