Energy drinks have a very high caffeine content because they combine natural caffeine from coffee beans as well as synthetic caffeine which is created in a lab.Here are energy drinks and their caffeine levels:– Find images + Caffeine levels in the caffeine calculator article we have published todaySome side effects of energy drinks include nervousness, restlessness, irritability, insomnia, headache nausea, heart palpitations (irregular heartbeat), and tremors (shakiness). But the most worrisome effect is that it may cause you to have an increase in your blood pressure which can lead to an increased risk of having a heart attack.If you're going to drink energy drinks, then it's best that you understand the caffeine amount of each type and how much caffeine is too much for you. Additionally, energy drinks contain a lot of sugar and tons of artificial ingredients, so it is important to also read the sugar content for each drink.The FDA has recently recommended more research on energy drinks as a concern as to whether or not they are safe for consumption.