For most people, having the occasional energy drink is not a problem, but there are some things you should be aware of. Most energy drinks contain large amounts of caffeine and sugar. Too much caffeine can lead to nervousness, insomnia, irritability, rapid heart beat and even increased blood pressure. The sugar found in energy drinks can also lead to weight gain unless consumed in moderation.
Mixing energy drinks with alcohol can also be an issue. The caffeine can reduce the feeling of intoxication, making many people drink more than they normally would. Energy drinks are fine to replace the occasional cup of coffee, but if you are tired all the time, talk to your doctor, as this could be the sign of a more serious medical condition.