Does Coffee Dehydrate You? We Asked Dietitians

It's not as detrimental to hydration as you might think.

Fact checked by Isaac Winter

According to the National Coffee Association, 62 percent of Americans drink coffee daily, with the average coffee drinker consuming more than three cups each day. Beyond its ability to wake you up, coffee has numerous health benefits, so it's no wonder it's a beloved beverage.

But if you tend to sip more coffee than water throughout the day, you might be asking the question: Does coffee dehydrate you? Read on to figure out exactly how your coffee habit is affecting your hydration levels.

Meet the Expert

• Ilisa Nussbaum, a distinguished Registered Dietitian Nutritionist certified by the state of Connecticut, is the owner of IN Nutrition.

• Marie A. Spano, MS, RD, CSCS, CSSD, is a leading sports nutritionist, having served major league teams, minor league affiliates, and MMA teams.
  

Regular Coffee Drinkers

"The impact of coffee on hydration is a super common question," says clinical dietitian Ilisa Nussbaum. "We always joke that nutritionists start each answer with 'it depends,' but it's true for this question."

If you're concerned about your morning cup of Joe, you need not worry too much. "Anyone who regularly consumes caffeinated coffee or tea will develop a tolerance, and a regular cup of coffee has no real significant effect on overall hydration status," says registered dietitian Marie Spano.

Studies have shown that drinking two to four cups of coffee (around an 8-ounce size cup—we're not talking Venti here) had little impact on hydration for the regular coffee drinker. The caffeine in coffee is a diuretic, but with regular consumption of coffee, that diuretic effect actually decreases, having minimal impact on urine output.

But don't mistake this information as a free pass not to hydrate in general. While coffee itself isn't too dehydrating, some frequent coffee drinkers should still hydrate in other ways.

"Don't let your caffeine intake impair your intake of straight fluids like water," Nussbaum says. Coffee may not dehydrate you detrimentally, and it can even count toward your daily hydration—but it's still imperative to drink enough water (and other more hydrating drinks) throughout the day.

Related: Exactly How Much Coffee You Should Be Drinking Each Day, According to a Recent Study

Casual Coffee Drinkers

While the diuretic effect of coffee decreases with regular coffee consumption, the casual coffee drinker may feel more of a dehydrating impact. They simply don't have the same level of tolerance as a more frequent coffee drinker. However, the impact isn't too intense. "In those who don't regularly consume caffeine, drinking two to three cups of coffee will lead to a very short-term and minimal increase in urine output," Spano says.

It's important to pay attention to what you feel like when drinking coffee. For example, if you're taking more trips to the bathroom (for number one or two), you may want to increase your fluid intake to replenish.

And when a habitual coffee drinker goes sans caffeine for a few days, they should treat it more like they're a casual drinker when they come back to it. "If you're sick or recovering from an illness that left you caffeine-free for a few days, it's a good idea to ease back into your coffee habit," Nussbaum says. Of course, whenever you're sick, it's important to hydrate as much as possible.

As for the decaf coffee drinker? Even decaf has trace amounts of caffeine, but it certainly has less of a diuretic effect than caffeinated.

Know Your Body

While coffee does have a diuretic effect, drinking one or two cups likely won't lead to dehydration. According to experts, you would have to drink more than 500 mg of coffee per day—about six cups— to induce a substantial amount of dehydration.

Nevertheless, everyone reacts to caffeine differently and has different hydration needs based on their size, age, and how much they exercise. Two cups of coffee may have little impact on one person, while another will feel more heightened effects. And not all cups of coffee have equal levels of caffeine—if you're noticing a pattern of adverse reactions, it's best to decrease the amount you're sipping.

"The easiest way is to pay attention to what your body feels like when you drink coffee: its impact on your sleep and the number of times you're going to the bathroom," says Nussbaum.

Tip

Start your day by drinking a glass of water to ensure hydration, regardless of when you enjoy your morning coffee.

Frequently Asked Questions

What is a diuretic?

A diuretic is a substance that expels salt and excess fluid out of the body. This is why it leads to increased urination. Caffeine serves as a diuretic by enhancing blood flow to the kidneys, which prompts the organ to release fluid through urine.

What type of coffee has the most caffeine?

The type of coffee with the highest caffeine content varies based on brewing method and bean type. Typically, a single shot of espresso contains around 63 mg of caffeine, while an 8-ounce cup of brewed coffee has around 70-140 mg of caffeine depending on the roast of the beans. Meanwhile, a 16 ounce serving of cold brew usually packs around 200 mg of caffeine, making it the coffee with the highest caffeine concentration.

Should you drink water before coffee?

Dietitians suggest enjoying coffee after hydrating with a glass of water and having some food. Due to the high acidity in most coffees, consuming it on an empty stomach may lead to stomach discomfort. Additionally, experts recommend maintaining proper hydration throughout the day after coffee consumption.

Can coffee cause electrolyte imbalance?

Research indicates that drinking coffee does not cause electrolyte imbalance. As long as you stay hydrated throughout the day, coffee consumption does not negatively impact exercise performance or overall health.

Related: 7 Delicious (and Healthy!) Ways to Upgrade Your Next Cup of Coffee

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