You have to admit it: energy drinks are convenient. If you feel hammered after a gym workout, are fading at the end of a long day at the office, or need a boost to get you through a long study session or meeting, you can just pop the lid or tab on an energy drink bottle or can and you’ll feel the energy flow in no time. The problem is, you’re getting much more than just an energy boost.

The makers of energy drinks say their products contain natural ingredients that can improve concentration, energy, attention, and sports performance. The most prominent ingredients are caffeine and sugar (with some products including artificial sweeteners); other ingredients may include ginseng, taurine (an amino acid), B vitamins, and guarana (which contains caffeine), among others. The ingredient posing the biggest problem is caffeine, although sugar isn’t so sweet either.

1 Energy drinks are not well regulated

Some energy drinks—but not all of them—are sold as dietary supplements, which means they are not well regulated by the Food and Drug Administration. The producers don’t need to provide a nutrition facts label on their products, so consumers can be left in the dark about what they are drinking.

2 Energy drinks are inaccurately labeled

Can consumers trust what energy drink makers say on their labels about caffeine content? According to a Consumer Reports study, no. Of 27 popular energy drinks evaluated, only 16 even listed the amount of caffeine on the label. Of those, five had more than 20 percent more caffeine that stated, and one had about 70 percent less. It’s anyone’s guess how much was in the 11 that did not even reveal the amount of caffeine. (You can see the actual amount of caffeine in the 27 products tested in a table in Consumer Reports.) Another concern is that some energy drinks may not factor in the caffeine in other ingredients, such as guarana.

3 Energy drinks contain LOTS of sugar

The sugar content of energy drinks can rival that of sugary sodas and fruit juices; that is, 25-plus grams per eight-ounce serving, which equals 6 teaspoons! The health dangers of sugar consumption are too numerous to list here, but some of them include the ability to promote aging, feed cancer cells, increase weight gain, and lead to chronic inflammation.

4 Energy drinks can affect your heart

Research shows that consuming more than 200 mg of caffeine can result in tachycardia (abnormally rapid heart rate) and arrhythmia (abnormal rhythm). That’s the amount of caffeine in one 5-Hour Energy Shot, and some products contain even more per serving. Drinking two or more other energy drinks that contain less than 200 mg per serving could lead to the same result.

5 Energy drinks don’t mix with alcohol

Combining energy drinks with alcohol is not uncommon, especially among young people. However, individuals who consume energy drinks and alcohol may be playing with fire. For example, a study from the University of Florida found that young adults who combined energy drinks with alcohol were three times more likely to binge drink and four times more likely to engage in reckless behavior (e.g., driving while drunk)

6 Energy drinks can affect your sleep quality

Individuals who use energy drinks risk suffering from poor sleep quality. A study in the journal Sleep & Breathing reported that college students who used energy drinks and other stimulants experienced poor sleep quality and increased daytime dysfunction due to sleepiness.