I’ve noticed more and more people drinking coffee before their workouts, in hopes that the caffeine will give them an energy boost to help them power themselves through their sweat sessions. It’s not surprising—there are plenty articles and studies discussing the positive effects of caffeine before a workout:

“Caffeine is a stimulant that acts on the central nervous system, the heart, and possibly the ‘center’ that controls blood pressure,” all of which play a vital role in helping your mind and body push harder in a workout, says Heidi Skolnik, M.S., a sports nutritionist and owner of Nutrition Conditioning, Inc. “It can also increase the release of feel-good neurotransmitters like dopamine, which effects pain receptors and mood” while you’re working out. [source]

She’s right, but—there’s always a but—there’s something else about it that concerns me a bit.

So many people already struggle to stay properly hydrated, and it’s a common occurrence to see people sidelined during a workout due to dizziness or sharp headaches or major cramping in random muscle groups. They never consider the fact that that pre-workout coffee could have something to do with it.

It cannot be forgotten that coffee is a diuretic—it helps you get rid of water your body holds onto for various reasons, including the general purpose bloating that happens around time for your menstrual cycle as well as “oh, I ate way too many fries last night and now have rings around my ankles” bloating related to salt intake. In other words, coffee—specifically when you drink a lot of it—will dehydrate you if you’re not careful. When you combine this with the already dehydrating nature of rigorous exercise, and you’re quickly depleting your body of the water it needs to keep you brain running the way it’s supposed to run.

Dehydration is serious business, especially when you add in heavy machines, heavy weights, fast-moving equipment, and large amounts of people. Workout spaces require the utmost of concentration and clear demarcations of personal space—think of how densely packed some of your favorite exercise classes are, or how tightly packed treadmills are in the gym. Now, imagine someone falling over on their spin bike because their lightheadedness that they ignored turned into a full-on faint. An unconscious person sent flying off the treadmill is no good—not for them, and certainly not for the people around them. We’re all already trying to cope with looking a mess in front of our fit-focused peers. Tripping over someone is pretty damn un-dope. It’s the anti-dope.

Not only does dehydration become a high risk during the workout, but after it, as well. A lack of fluids also translates to a lack of electrolytes pretty quickly—water, salt, sugar, potassium, calcium, magnesium, phosphate are your electrolytes—which means you’re now running a pretty high risk of post-workout cramping, and Whooooooooooooooooooooooooooo lawd that’s the worst thing you want to experience after winding down from an intense workout.

If you’re going to drink caffeine prior to a workout, you need to be strategic. Make sure you are thoroughly hydrated the night before your workout—in other words, the color of your pee shouldn’t be anything darker than a faint yellow when you look in the toilet after you’re finished—and, on top of keeping your post-workout nutrition on point, make sure that you replenish any fluids you lost during the workout. The introduction of a diuretic, a dehydrating agent, to the equation makes the risk of injury especially high.

Most important of all, if you want to utilize caffeine as a pre-workout boost, know the signs. If you’re feeling lightheaded, things start to get a bit blurry, if you’re feeling dizzy, developing a sharp headache, if you start to feel shooting pains in any part of your body—and, by shooting pains, I mean the kind that feel like they’re traveling from one part of your body to the next— or feel a muscle squeezing in a way that isn’t helping you execute your exercise, then stop and sit down, and ask an attendant for two glasses of water, and down them without hesitation. People with heart conditions or excessively high blood pressure should avoid this at all costs—if your heart is already having a relatively hard time getting oxygen throughout your body, adding a stimulant that increases your heart rate might only make things worse. Definitely get the OK from your doctor before giving it a shot.

I’m totally in favor of a pre-workout coffee. I personally get a shot of espresso and add cream and a little simple syrup before my spin classes. It’s helpful because not only will it help me get a boost during my workout, but also because the sugar and cream—not a lot, just maybe a teaspoon of simple syrup and a couple tablespoons of cream—will help me with making sure I’m not so depleted post-workout that I feel the need to eat everything in sight post-workout.

If you’re an evening exerciser, be careful that you don’t drink so much coffee that you’re negatively impacting your sleep to get in a better calorie burn. I know that some exercises will exhaust you regardless of whether or not you had caffeine, and send you crawling to your bed, but if you’re not that kind of exerciser, then just opt for the usual pre-workout fuel to ramp you up and get you ready.

Experimentation is important, but so is self-care. Make sure that you pay close attention to your internal signs, and ditch the things that don’t work for you. As I always say, your body will thank you for it!