A lot. A 2012 Consumer Reports article, “The buzz on energy-drink caffeine,” found that some 12 or 16-ounce energy drinks contain as much as 242 mg of caffeine—nearly three times the amount in a cup of coffee. A two-ounce 10-Hour Energy Shot contains 422 mg. And these numbers don’t even account for these drinks’ excessive sugar content, or other stimulants like guarana.
Though the American Beverage Association encourages it, the FDA does not require energy drink companies (or anyone else) to disclose how much caffeine is in their products because dietary information is only required for nutrients, while caffeine is a “natural chemical.” This allows energy drinks to conceal or undersell their caffeine content—legally.
When energy drinks first came under fire a few years ago—with doctors and lawmakers pushing for more transparency and regulation in response to the deaths of 19-year-old Alexis Morris and 14-year-old Anais Fournier, among others—Monster and other drink manufacturers agreed to disclose their ingredients and add labels displaying the quantity of caffeine, sugar, and other stimulants. Unfortunately, because the FDA does not require them, it also does not test or analyze these caffeine levels (or taurine levels, or guarana, etc.) for accuracy.
In January 2013, in response to its own spate of energy drink-related deaths and other adverse events, Canada capped the caffeine levels allowed in single-serving beverages at 180 mg. To do so, it forced 28 companies—including Monster, Red Bull, Rockstar, and 5-Hour Energy—to reclassify as food products. (They had previously been regulated as “natural health products.”) Canada also requires labels to disclose the amount of caffeine per serving, and to include warnings for use by children and sensitive adults.