Energy drinks may raise blood pressure and prolong QT interval increasing the risk of sudden cardiac death.

In a meta-analysis by Sachin A. Shah at University of the Pacific in Stockton, Calif, with a pooled analysis of 93 people who consumed energy drinks, the QT interval on an ECG was significantly prolonged by 10 ms. The threshold level of regulatory concern is around 5 ms.

In another pooled analysis of 132 people by the same group, researchers found a significant increase in systolic blood pressure by 3.5 mmHg that was associated with the consumption of energy drinks.

Doctors are generally concerned if patients experience an additional 30 ms in their QT interval from baseline. QT prolongation is associated with life-threatening arrhythmias.

Most energy drinks have caffeine. Drinks such as Monster, Red Bull, Rockstar, Full Throttle and AMP have three times the amount of caffeine as colas. A 16-oz. can of Monster Energy, for example, contains 160 mg of caffeine, which is almost as much as 5 cans of soda.