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How do you prepare for a big exam? Do you listen to classical music, chug caffeine, or pull an all-nighter to cram for the exam? Forget every pre-test ritual you’ve adhered to in the past. All you need to ace your next big exam is some H2O. According to a 2012 study led by Doctor Chris Pawson at the University of East London, drinking water prior to an exam may increase your academic performance.

Over the course of the study, researchers observed a total of 447 undergraduate students in an exam environment. Taking note of which students drank water during the exam, researchers were able to determine that students who drank water improved their scores by up to 10% and performed an average of 5% better than students who did not drink any water.

While you may not realize it, dehydration causes more than just thirst. Water plays an important role in the function of our cells, tissues and organs—including the brain. Water transports oxygen to the brain, which allows it to communicate important messages to the rest of the body. Even the slightest lack of hydration can reduce your concentration and impair your ability to think clearly and perform well.

Dr. Pawson also suggests taking a sip of water during a high-stress situation, such as taking an exam, may help reduce anxiety. He explains that pausing to take a drink of water is a distraction that allows individuals to briefly clear their mind of nervous thoughts and get back to the task at hand. Staying adequately hydrated also prevents headaches, which can also hinder your concentration and execution on a test.

To keep your brain functioning on all cylinders, physicians recommend drinking at least half of your body weight in ounces of water each day. For example, if you weigh 150 pounds, you should be consuming at least 75 ounces of water daily, or approximately four-and-a-half water bottles.

While additional research is still needed to uphold these claims, there is clearly a link between hydration and performance, both mentally and physically. And, the good news is these findings extend well beyond test scores. So, if you have an upcoming interview, a big presentation or an important meeting, drink up!