Caffeine: How much is too much? – Mayo Clinic
According to the Mayo Clinic (link below article):
“Up to 400 milligrams (mg) of caffeine a day appears to be safe for most healthy adults. That’s roughly the amount of caffeine in four cups of brewed coffee, 10 cans of cola or two “energy shot” drinks. Keep in mind that the actual caffeine content in beverages varies widely, especially among energy drinks.
“Caffeine in powder or liquid form can provide toxic levels of caffeine, the U.S. Food and Drug Administration has cautioned. Just one teaspoon of powdered caffeine is equivalent to about 28 cups of coffee. Such high levels of caffeine can cause serious health problems and possibly death.
“Although caffeine use may be safe for adults, it’s not a good idea for children. Adolescents and young adults need to be cautioned about excessive caffeine intake and mixing caffeine with alcohol and other drugs.
“Women who are pregnant or who are trying to become pregnant and those who are breast-feeding should talk with their doctors about limiting caffeine use to less than 200 mg daily.