Introduction: Energy drinks are presumed to enhance energy, physical endurance, mood, and boost metabolism. Serious health risks have been reported with energy drink consumption such as myocardial infarction, cardiac arrest, stroke, seizures, and arrhythmias. More than 20,000 emergency department visits related to energy drink consumption were reported in 2011. Little is known about the possible pathophysiological mechanisms and adverse events associated with energy drinks. Unlike the tobacco and alcohol industry, there are limited restrictions regulating the purchasing and marketing of these drinks. Purpose: To determine if consumption of energy drinks alter; vital signs (blood pressure, temperature), electrolytes (magnesium, potassium, calcium), activated bleeding time (ACT), or cardiac responses measured with a 12-lead electrocardiographic (ECG) Holter. Method: Subjects consumed two-16 ounce cans of an energy drink within one hour and remained in the lab where data was collected at base line (BL) and then during four hours post consumption (PC). Vital signs were taken every 30 minutes; blood samples were collected at BL, one, two and four hours PC and ECG data was collected throughout the entire study period. Paired students t-test and a corresponding non-parametric test (Wilcoxon signed rank) were used for analysis of the data. Results: Fourteen healthy young subjects were recruited (mean age 28.6 years). Systolic blood pressure (BL=132, ±7.83; PC= 151, ±11.21; p=.001); QTc interval (BL=423, ±22.74; PC=503, ±24.56; p500 milliseconds PC. Conclusions: In our sample, consumption of energy drinks increased systolic blood pressure, serum magnesium and calcium, and resulted in repolarization abnormalities. Because these physiological responses can lead to arrhythmias and other abnormal cardiac responses, further study in a larger sample is needed to determine the effects and possible consequences of energy drink consumption.