By Elise Viebeck - 01/17/13 10:49 PM EST
A report released last week by the Substance Abuse and Mental Health Services Administration found that the number of emergency room visits tied to energy drinks had doubled in the last five years.
Reports last fall tied a number of deaths to the drinks as well, though manufacturers have denied the connection.
In their letter, Markey, Durbin and Blumenthal asked companies to describe the level of caffeine and other stimulants in their beverages, and explain whether they consider their products conventional beverages or dietary supplements.
"Currently, manufactures have the discretion to decide whether an energy drink product will be marketed and labeled as a conventional food (beverage) or as a dietary supplement," the lawmakers wrote.
The difference determines "requirements for ingredients, manufacturing processes, [and] reporting of adverse events and labeling," the members wrote.
Experts say a serious caffeine overdose can lead to elevated blood pressure, cardiac arrhythmia or arrest, and seizures.