how much caffeine do i need to stay up?
Most people need about 100 milligrams (mg) to 200 mg of caffeine, depending on their body weight, Rosekind says. (Coffee has about 100 mg of caffeine in a 5-ounce cup, though the content varies based on the strength of the brew.) Over-the-counter caffeine pills also are available in 100 mg or 200 mg doses.