A recent government report found the number of visits to emergency facilities linked to energy drinks doubled from 2007 to 2011.
During that time, the Food and Drug Administration banned one drink that mixed caffeine and alcohol, called Four Loko.
Just one energy drink can be equal to five cups of coffee. Many of those who went to the emergency room said they drank as many as four energy drinks in a single day. Having that much caffeine, especially in such a short period of time, can cause cardiovascular problems, such as fast or irregular heartbeat.
Of the nearly 21,000 people who went to the ER with similar symptoms, about 70 percent were men and 42 percent mixed energy drinks with drugs or alcohol. So we asked a local doctor how much is safe to drink.
"Two cups of coffee, up to four cups spread throughout the day, is reasonable. Throw in a soda on top of that or energy drinks on top of that, then it's too much," said Dr. Cam Campbell, Medical Director of Cardiovascular Services at Mercy Medical Center in Cedar Rapids.Doctors say if you have pre-existing conditions, such as heart problems, you are even more at risk of complications and should avoid high levels of caffeine.