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Does Coffee Dehydrate You? Caffeine Effects Explained

drinking bottled water

How often have you heard someone tell you to go easy on the coffee when the weather is hot? This warning is usually due to the belief that coffee dehydrates the body making you more likely to become ill during the summer. Is this true, though?

In the article below, we will answer this question, and go over all the details and research. If you have ever wondered whether you have to drink equal parts water to coffee or if you should be drinking it at all, we have you covered. The surprising answer is that coffee does not dehydrate you!

Besides those main points, we will also go over who should drink coffee and who should steer clear. Keep scrolling for all your coffee dehydrating coffee questions below.

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Is Coffee Dehydrating you?

According to the Mayo Clinic, no, it isn’t. As the Mayo Clinic has reported, coffee doesn’t cause a loss of fluid above what is ingested. This pretty much means that the amount of coffee consumed is not equal to the amount of fluid loss in the body. To put it even more simply, drinking coffee doesn’t mean you will lose fluid.

That being said, everyone is different and processes coffee and caffeine differently. Not only that, but coffee is a diuretic. To get a full understanding of how coffee works in the body, it’s important to understand what dehydration and diuretics mean for you.


The Oxford dictionary defines dehydration as, “the loss or removal of water from something.” When it comes to the human body, it means that you have lost enough fluids without replacing any that it’s affecting the body.

Image Credit: RobinHiggins, Pixabay

Dehydration can be caused by many things including exercising without getting the proper amount of water, being out in the hot sun too long, and beverages such as alcohol. Allowing your fluids to run low causes many issues ranging from mild to serious. Take a look at these symptoms of dehydration:

  • Thirst
  • Dry mouth
  • Less urination
  • Dark yellow urine
  • Dry and cool skin
  • Headache
  • Muscle cramps
  • Dizziness
  • Rapid heartbeat
  • Fainting
  • Rapid breathing
  • Sunken eyes

All of these symptoms are due to a lack of fluids in the body, but they don’t end here. Dehydration can also cause high temperatures, cardiac problems, and in extreme cases, death. The symptoms above are the body’s way of telling you that it’s time to drink water.


Although it is often associated with dehydration, a diuretic is quite different. It is something that reduces water in the body. It can be a beverage like coffee, or it is sometimes given as a pill to help with high blood pressure and other ailments.

Coffee, rather than caffeine, is a diuretic. In this case, it’s causing the kidneys to produce more urine. This is why a lot of coffee drinkers (especially new coffee drinkers) report having to use the bathroom more frequently when drinking it.

While studies have been done, scientists are not sure how or why caffeine works as a diuretic, but the result is true, nonetheless. This is also why coffee consumption is often paired with dehydration. If you are constantly having to use the bathroom, wouldn’t that mean you are losing more water than you can take in? Not necessarily.

The Research

One reason that people fear drinking coffee may lead to dehydration is because of a 1928 study that showed people who drank caffeinated beverages urinated 50% more than those who didn’t. What they were not looking at was the liquid intake versus the output.

coffee aroma
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Many variables come into play when it comes to caffeine and the effects it has on the body. That being said, many studies have shown that the amount of liquid “water” you take in when drinking a caffeinated drink isn’t reduced by the diuretic effect.

Study 1 – In this study, researchers point out that you need to consume more than five cups of coffee per day for it to affect your hydration levels. You would have to consume quite a bit more to send yourself into a severe dehydration scenario.

Study 2 – In another study, participants showed that drinking 26.5 ounces of coffee per day was just as hydrating as drinking water. This test was done with people who are considered to be moderate to heavy coffee drinkers.

Study 3 – According to Dr. Daniel Vigil of UCLA Health, there is typically no difference in hydration between drinking coffee and drinking water. Where the difference comes in is with the individual person along with the diuretic effect.

How Caffeine Affects Different People

As you noticed above, one of the recurring themes is how caffeine affects the individual. It has been noted that people who drink coffee, and other caffeinated beverages, regularly don’t feel the diuretic effect as much as those who only drink coffee occasionally. This can make a difference in how dehydrating the drink is, as well.

Another study concluded that when a regular coffee drinker stopped consuming the beverage for four days or more, when they started back up the need to use the bathroom was increased. Not only that, but your genes can also play a role.

Everyone has a genotype that determines the body’s ability to metabolize caffeine. If you can process it quicker, you are more likely to fair better. Some people are also predisposed to dehydration. This can play a role, too.

coffee and water
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Hydrating with Coffee

With all of the variables above, how do you know whether coffee will harm your body and hydration? This can be a difficult question to answer, but if you already drink the brew you likely know the answer. If you don’t, you should monitor how you feel for signs of dehydration.

It is also thought that women going through their menstrual cycle can experience different effects of caffeine due to the fluctuation in body fluid. Although coffee may not bother them normally, during this time it can cause side effects.

The long and short of it is, while caffeine may not dehydrate you, it should not be used as a substitute for water. Nothing is as good as gold old H2o when it comes to increasing hydration in your system. Beyond that, the US Department of Agriculture Dietary Guidelines indicates that you shouldn’t consume more than three to five 8-ounce cups of coffee per day.

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Coffee & Dehydration: The Surprising Conclusion

So, as it turns out, coffee is not the big bad water thief we all thought it to be. You can stay hydrated by drinking the popular beverage a few times each day. Of course, that doesn’t mean the statistics on the benefits of water don’t count or that you shouldn’t listen to your body. At the end of the day, however, having that much-needed afternoon pick me p is not going to harm you in the way of hydration.


Featured Image: Peggy_Marco, Pixabay


Kate MacDonnell

Kate is a lifelong coffee enthusiast and homebrewer who enjoys writing for coffee websites and sampling every kind of coffee known to man. She’s tried unusual coffees from all over the world and owns an unhealthy amount of coffee gear.

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