Just two energy drinks a day can be bad for your heart, a new study has warned.
The drinks, many packed with sugar and caffeine, can trigger abnormal heart rhythm and a rise in blood pressure.
This increases the risk of stroke and sudden cardiac death.
And the effects last over two hours after having the drink.
Scientists from the University of the Pacific and David Grant Medical Centre, in the US, warned these energy drinks have been linked to at least 34 sudden deaths up to 2014.
Sachin Shah, associate professor of pharmacy practice at Pacific's Thomas J Long School of Pharmacy and Health Sciences said: "Our findings suggest certain energy drinks may increase the risk of having an abnormal heart rhythm when consumed in high volumes.
"While we wait for more data, some consumers should exercise caution and not blindly follow the buzz."
The study involved 27 healthy volunteers aged 18 to 40 who either drank two cans of an energy drink, an equivalent volume of a drink containing panax ginseng - an ingredient in the energy drink - or a placebo beverage once a day, every six days, for three weeks.
The researchers measured subjects' heart rhythm and blood pressure before the drinks were consumed and four times during the six hours immediately afterwards.
The volunteers who consumed the energy drink experienced a statistically significant increase in a marker of abnormal heart rhythm risk known as the QTc interval.
These volunteers also experienced a slight rise in blood pressure.
These effects persisted for two hours after the energy drink was consumed.
In contrast, the ginseng and placebo groups showed no rises in QTc interval or blood pressure.
Phillip Oppenheimer, dean and professor of pharmacy practice at Pacific, said: "Energy drinks are widely consumed within the college population, which further extends the relevance of this study."
Prof Shah noted that some drugs contain a warning in their package insert when the drug has been shown to prolong the QTc interval to a degree similar to that seen in the study - 6 milliseconds.
He added more research was needed to assess the heart rhythm and blood pressure effects of energy drinks, especially in those with underlying cardiac conditions such as congenital long QT syndrome and hypertension.
The findings of the study was presented at a meeting of the American Heart Association in Phoenix, Arizona.