Is Coffee Hydrating or Dehydrating?

  • Medical Reviewer: Mahammad Juber, MD
Medically Reviewed on 10/19/2022

What is dehydration?

Dehydration occurs when your body loses more fluid than it gets, affecting some critical functions in your system. Coffee has a mildly dehydrating effect due to its caffeine content.
Dehydration occurs when your body loses more fluid than it gets, affecting some critical functions in your system. Coffee has a mildly dehydrating effect due to its caffeine content.

Did you know that the word “coffee” is derived from an Arabic phrase that means “wine of the bean,” while cappuccino was named after the Capuchin Friars due to the drink’s resemblance to the clothing of these monks? Several drinks prepared from coffee beans are immensely popular across the world, but what is less commonly known is that coffee has a diuretic effect on the body. Based on that, you may be wondering – does coffee dehydrate you?

Dehydration occurs when your body loses more fluid than it gets, affecting some critical functions in your system. If you don’t give your body enough fluids to replace the ones it has lost, that could lead to dehydration

Some of the common symptoms of dehydration in adults include:

Young children may get dehydrated due to conditions such as diarrhea and vomiting

Meanwhile, older adults commonly have lower levels of fluids in their bodies to begin with. They may consequently face an increased risk of dehydration if their fluid intake is reduced or if they receive certain medications.

You can get dehydrated irrespective of age, though, especially if your fluid intake is low in hot weather, you’re feverish, or you’re exercising and sweating intensely. You can typically overcome dehydration by drinking more fluids. However, severe conditions may require swift medical attention.

Does coffee dehydrate you?

One of the primary reasons people drink coffee is to get their daily caffeine fix. Caffeine is the world’s most widely consumed psychoactive substance. This compound has been linked to increased physical endurance, lower fatigue, and enhanced mental alertness.

Once caffeine enters your body, it passes through the gastrointestinal tract. Then, it enters the liver through the bloodstream. Caffeine is subsequently broken down into multiple compounds by the liver, affecting your brain functions. Research shows that in addition to the molecules that affect brain functions, caffeine also contains a diuretic that affects your kidneys, especially when taken in high doses.

Diuretics are substances that make your kidneys expel more water from your body. While diuretics are a good option to lower your blood pressure, high amounts of diuretics could lead to too much water loss and dehydration.

Caffeine increases the blood flow to your kidneys, stimulating them to release more water through the urine.

How much caffeine does coffee contain?

The caffeine content in coffee depends on the preparation method, impacting its dehydrating effects. 

Some of the most common types of coffee and their caffeine content are listed below.

Brewed coffee

The standard method of making a coffee brew combines one or two tablespoons of ground coffee powder with six ounces of water. These amounts, though, can be modified to suit your taste. You can either buy ground coffee or a preferred strain of coffee beans, roast them, and grind them to get the powdered form, which you can use to brew your drink. One cup of brewed coffee typically contains around 95 to 100 milligrams of caffeine.


Espresso is prepared by forcing a small amount of very hot water through finely-ground coffee beans. The green coffee beans are first roasted and ground into a fine powder before extracting the beverage under extreme pressure. A cup of espresso (eight fluid ounces) contains around 200 to 250 milligrams of caffeine.


Decaf means coffee that is decaffeinated. It’s usually prepared using coffee beans with roughly 97% of their caffeine content removed. Four different processes are used to remove the caffeine from the coffee while the beans are still green. A regular cup of coffee contains around 95 milligrams of caffeine, whereas decaf contains only about two milligrams.

Instant coffee

Instant coffee is a soluble coffee that can be directly mixed with water or milk. Making instant coffee involves first roasting the coffee beans and then brewing them in hot water. This mixture is then dried by either spray-drying or freeze-drying the brew.

To make this beverage, add one or two teaspoons of the instant coffee powder to a cup of hot water and mix them to dissolve the powder. A single cup of instant coffee typically contains around 60 to 65 grams of caffeine.

Drinking some types of coffee may not cause dehydration

While a hot cup of coffee would likely not be your first choice after a rigorous workout, it’s not the worst thing you could drink. Caffeinated beverages such as coffee and tea have long been thought to have a dehydrating effect due to their caffeine content, but this is not necessarily accurate. While caffeine has a minor diuretic effect, only some types of caffeinated drinks are likely to dehydrate you.

Research shows that you’ll need to take more than 500 milligrams of caffeine for it to have any noticeable diuretic effect. This is equivalent to almost eight fluid ounces of espresso or 40 fluid ounces of brewed coffee.

A 2017 study involving 10 coffee drinkers compared the effects of drinking 200 milliliters of water, low-caffeine coffee (containing 269 milligrams of caffeine), and high-caffeine coffee (containing 537 milligrams of caffeine). The study found that drinking high-caffeine coffee had a short-term dehydrating effect, while low-caffeine coffee and water had a hydrating effect.

Another 2014 study involving male coffee drinkers who took three to six cups of coffee every day found that drinking 800 milliliters daily for three days hydrates your body just as much as the same quantity of water would. A separate 2015 review indicated that drinking roughly 300 milligrams of caffeinated drinks at once (around 700 milliliters of coffee) led to only a 3.7-ounce increase in urination compared to drinking non-caffeinated beverages.

All the research suggests that drinking regular coffee should not cause dehydration, as your body doesn’t lose too much fluid. An espresso, however, may be a different story.


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Medically Reviewed on 10/19/2022

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