Does caffeine dehydrate you?

Photo by  Dan Gold  on  Unsplash

Photo by Dan Gold on Unsplash

I personally drink coffee everyday. Perhaps I am addicted. Or perhaps I love the ritual it brings to my life. Rolling out of bed, groggily slipping downstairs, heating a kettle, grinding the beans, adding the perfect amount of almond milk, taking the first steaming hot sip as I stare semi aimlessly out my kitchen window, catching the first rays of sun as they rise over my neighbors’ homes.

There is a lot to write about in regards to coffee. Today I want to focus on a common misconception: coffee, or caffeine, dehydrates you. Honestly, I wouldn’t be surprised if researchers found a positive correlation, ultimately advising the public to stay clear of caffeine in all forms. However, I’m here to report caffeine does not dehydrate you!

In fact, the Academy of Nutrition and Dietetics covered this topic in their Evidence Analysis Library (EAL). The EAL is a cool tool I’m able utilize as a dietetic student. Essentially it is a combination of the highest quality and most pertinent nutrition research gathered in one place to answer the most significant dietetic practice questions. One topic covered is hydration, more specifically how caffeinated beverages affect the fluid needs of adults.

In total, ten studies were assessed to answer the question: “How do caffeinated beverages affect the need for other fluids in adults?” As I alluded to above, the EAL concluded moderate caffeine consumption does not impact the hydration status of healthy adults. Perhaps surprisingly, the EAL actually came to this conclusion: adults may consume up to six milligrams of caffeine per kilogram of body weight per day without affecting hydration status. To put this in perspective, a home brewed eight ounce cup of coffee contains 95-165 mg of caffeine. Comparatively, a sixteen ounce Pike Place Roast from Starbucks contains 310 mg of caffeine. Now, you may be asking… how do I convert pounds to kilograms and then kilograms to milligrams?? To determine kilograms, simply divide your body weight in pounds by 2.2. Next, multiply your body weight in kilograms by 6 to determine milligrams of caffeine per day. [For an example, take a look at the image below!]


Out of the ten studies assessed, I found one in particular worth sharing. To determine whether chronic caffeine consumption reduced level of hydration, researchers pulled together fifty-nine, relatively healthy, male college students. The men were split into three groups and given 3 mg of caffeine per kg of body weight per day for six days. Following the six days, they were randomly assigned 0, 3, or 6 mg of caffeine per kg of body weight per day for another six days. Concluding the study, researchers determined no significant differences in physiological or fluid-electrolyte measurements.

Although these results are affirmative for coffee drinkers, I believe more research is needed on the subject. You see, the majority of these studies assessed healthy, active, young adult males. Although I don’t see why the results of females would differ by too much, I would be interested to read such outcomes in the future. I also wonder how results would vary by age, health status, and duration of caffeine consumption. That being said, the conclusion drawn by the Academy of Nutrition and Dietetics EAL is highly reliable, and definitely pertinent to consider if you at any time have questioned the consequences of caffeine consumption.

To conclude, I hope this cleared up some confusion on the topic of caffeine and hydration. I will leave you with this final thought: yes, caffeine may not dehydrate us, but that does not mean coffee or tea should replace your water intake! Something I didn’t mention earlier— my morning actually starts with big big big gulps of water. Personally, that’s what my body really needs first thing in the morning.

Until next time, stay hydrated friends :)


Evidence-based Nutrition Practice Guideline on Hydration published 2007 at and copyrighted by the Academy of Nutrition and Dietetics. Accessed 24 February 2019.

Roti MW, Casa DJ, Pumerantz AC, Watson G, Judelson DA, Dias JC, Ruffin K, Armstrong LE. Thermoregulatory Responses to Exercise in the Heat: Chronic Caffeine Intake Has No Effect. Aviat Space Environ Med. 2006 Feb; 77 (2): 124-129.

Caffeine | Center for Science in the Public Interest. Accessed February 25, 2019.

Caffeine content for coffee, tea, soda and more. Mayo Clinic. Published April 14, 2017. Accessed February 25, 2019.