With today’s non-stop, high-stress lifestyle, it’s no wonder that energy drinks have become one of the most popular beverages in the US. The afternoon dose of a caffeine-laden beverage is a ubiquitous part of office culture. It can be a much-needed boost to get through the work day, a way to power through a sweat session at the gym, or a lifeline to fuel a late-night exam cram. Energy drinks are a quick caffeine fix with the grab-and-go convenience of a can. But when it comes to energy drinks and health, too much of a good thing can have some nasty side effects.

Not as Healthy as You Thought

The basis for most energy drinks is a heaping dose of caffeine. Though the FDA limits soda to a maximum of 71 mg of caffeine per can, there is no such limit on energy drinks because they aren’t classified as sodas. Of course, part of the appeal of drinks like Monster and Red Bull is that they offer more than just a caffeine jolt. Many claim to be packed with vitamins and minerals so that they sound like a healthy choice. Most energy drinks contain an amino acid called taurine, which may boost athletic performance according to some studies. Because it’s classified as a dietary supplement, the long-term effects of taurine use have not received much scrutiny. A lot of these purportedly healthy beverages are also loaded with sugar.

The Dangers of Too Much Caffeine

While caffeine-laced beverages are fine in moderation, too much caffeine can have negative side effects in both the short term and long term. A 12-ounce cup of black coffee contains about 260 milligrams of caffeine. Red Bull and Tab Energy each have less than 100 mg per serving, while Monster, Rock Star, and No Fear keep it below 200. Caffeine toxicity can occur at 500 mg of consumption, and two energy drinks on the market, Fixx and Wired X505, dish out at least this much caffeine per serving.

Symptoms of moderate caffeine toxicity include nervousness, headache, nausea, irritability, and insomnia. Serious caffeine overdose can cause accelerated or arrhythmic heartbeat, hallucinations, tremors, and convulsions. Too much can even prove fatal: medical professionals linked energy drinks to 18 deaths between 2004 and 2012.

Energy Drinks Give Sleep a Tough Workout

Energy drink consumption can have a negative impact on the quantity and quality of your sleep, which in turn can affect other aspects of your health. The US Military studied the effects of energy drinks on service members, and the results were alarming. While 45 percent of those surveyed said they consumed one energy drink per day, 14 percent admitted to slugging back three or more daily. Those in the three-a-day group were found to average less than four hours of sleep per night. Because of their disrupted sleep patterns, these service members also experienced daytime exhaustion and falling asleep on the job. This study illustrates the vicious cycle of too much caffeine: the service members who chug the drinks by day to make up for the sleep it causes them to lose at night.

Consume in Moderation

Energy drinks, like many other substances, are fine in moderation but potentially dangerous when used irresponsibly. Most people can drink one or two of these beverages on a daily basis with no problem. Keep an eye on your daily caffeine intake, and dial it back if you’re experiencing some of the negative side effects of energy drinks. If you’re having trouble sleeping, consider cutting off your caffeine consumption at least six hours before you need to fall asleep. And you may want to pass altogether on those energy drinks that serve up automatic caffeine overdose in a can.