When we hit that 3 pm energy slump or our college kids need to pull off a late-night study session, we’re often tempted to drink a can of Red Bull, Rock Star, or Monster. Is that safe?

The buzz energy drinks provide comes from large doses of caffeine and other legal stimulants like guarana and ginseng. In fact, energy drinks can contain 75 mg to over 200 mg of caffeine per serving – or the equivalent of one or two cups of black coffee. Caffeine free drinks derive the energy boost from guarana, which has the same effect as caffeine. The amount of caffeine or stimulants may actually be higher if the can contains two or more servings.

Is it okay to drink an occasional can when you need to stay up late? Caffeine is a powerful substance that should be treated with care. The stimulating properties in energy drinks can raise heart rate and blood pressure, sometimes causing palpitations. The substances also dehydrate the body and may cause problems with sleep.

What about using energy drinks for an energy boost before you hit the gym or jog? When you’re sweating from exercise and experiencing the diuretic effect of caffeine, you may become severely dehydrated.

Energy drinks have become a popular mixer with alcohol, which presents more potential dangers. Combined with alcohol, which is a depressant, stimulants may mask how intoxicated someone is. Fatigue is a warning sign of intoxication. No matter how alert you might feel after drinking a Red Bull with vodka, the blood alcohol is the same as it would be without the energy drink. Once the stimulant wears off, the alcohol effects remain. Research also has shown that people drink more and have higher BAC levels when they combine alcohol with caffeine. Energy drinks and alcohol are both dehydrating, which can impact your body’s ability to break down alcohol, increasing the toxicity.