Does coffee dehydrate you?

Here is what you should know about your daily cup of joe

By Jennifer Billock | Oct. 10, 2023 Medically reviewed by Chad Shaffer, MD

If you’ve ever guzzled one too many cups of coffee, you may be worried about the caffeinated elixir dehydrating you. After all, it does have diuretic properties. But really, the relationship between caffeine and hydration is more complicated.

Dehydration happens when you don’t have enough water in your body. When dehydrated, you may experience fatigue, cramping, dizziness and confusion—symptoms no one wants when they need an afternoon pick-me-up. So, does coffee dehydrate you? Here is what experts say.

Does coffee dehydrate you?

Whether or not coffee dehydrates you is a more complex question than you might think. In the past, the prevailing narrative was that yes, it does—but modern research has proven mostly otherwise.

“There has been some debate about whether coffee has a dehydrating effect due to its diuretic properties, which can increase urine production,” says David Cutler, MD, a family medicine physician at Providence Saint John’s Health Center in Santa Monica, California. “However, the impact of coffee on hydration is generally considered less significant than once believed.”

Today, most providers agree that coffee isn’t “bad” for dehydration. Although it can have a short-term dehydrating effect, it most likely won’t put you into a significantly dehydrated state. “While coffee may increase urine output temporarily, it doesn’t necessarily lead to chronic or significant dehydration in people who consume it in moderation,” Dr. Cutler says. “The net effect on hydration depends on various factors, including the amount of coffee consumed and an individual’s overall fluid intake.”

Whether coffee dehydrates you depends on how much you drink, how your body reacts to caffeine in general, and the type of coffee you drink.

Amount of caffeine

The diuretic properties in coffee come from the caffeine, which is both a stimulant and something that makes you want to urinate. So, the more coffee you drink, the higher your caffeine intake, and the greater the diuretic effect and fluid loss will be. You can have one cup of coffee and experience a mild diuretic effect. But drinking several shots of espresso or 20 cups of coffee in one night will hit you a lot harder because the milligrams of caffeine are so much more pronounced.

Frequency of coffee consumption

As for how your body reacts to caffeine, it depends on how often you drink coffee or other caffeinated drinks, Dr. Cutler explains. “Regular coffee drinkers may develop a certain degree of tolerance to the diuretic effect of caffeine over time,” he says. “This means that the impact on hydration may be less pronounced in individuals who consume coffee regularly.”

Type of coffee

Finally, the type of coffee drink is important to consider because the water content of different caffeinated beverages varies. “The hydration impact of coffee can also depend on the water content of the coffee beverage itself,” Dr. Cutler says. “If you’re drinking black coffee, it contains water, which contributes to your overall fluid intake. However, if you add significant amounts of sugar and cream to your coffee, the diuretic effect of caffeine may outweigh the hydrating effect of the water content.”

So, while it’s generally assumed safe to drink coffee and not risk dehydration, that doesn’t mean it’s safe to completely eliminate water from your daily fluid intake. If you drink only coffee and no water, you could become dehydrated. So, as long as you balance your coffee consumption with more hydrating drinks, like water, you should be okay to consume a moderate amount.

Does coffee count as water intake?

Now that you know that there is no evidence of dehydration from your daily coffee intake , you may be wondering if your venti cold brew could actually help with your hydration status. No, says Hannah Goldberg, MD, a primary care physician at Mercy Medical Center in Baltimore, Maryland. She says coffee should not count toward your daily water intake, which is 125 ounces for men and 91 ounces for women. Your specific goal for daily fluid intake will depend on size, activity level, and other factors.

Dr. Goldberg explains that because caffeine is a diuretic, “it causes you to lose more water from your kidneys in the form of urine. So even though you’re drinking a larger volume of liquid, your body may excrete more volume than you consumed from the coffee.”

The diuretic effect of caffeine does stimulate your kidneys to flush out extra sodium and water, but because the effect is mild and short-lived, you don’t need to worry about any (current or lasting) kidney damage. In other words, coffee does not dehydrate your kidneys.

But to help your kidneys and your overall health, you should try to achieve your daily water intake through water and other hydrating beverages—not coffee.

Should I avoid coffee if I am dehydrated?

Generally speaking, you don’t absolutely have to avoid coffee if you’re dehydrated, but it is not your best choice. While it may not make your hydration levels significantly worse than they already are, it will not help matters. Instead, drinking more water is a better decision, or even better yet, drink a balanced water, sugar, and salt solution, such as Pedialyte.

When you’re dehydrated, you’re already at a water deficit. As Dr. Goldberg mentions, caffeine is a diuretic and causes you to lose more water than usual. Whatever hydrating water your body has left could be flushed out on your next visit to the restroom after drinking a cup of joe.

So while it’s unlikely that caffeine consumption while you’re dehydrated will cause serious issues, it might not be worth it to take the chance. If you drink coffee when you’re dehydrated, you may experience more pronounced symptoms like dizziness, brain fog, and a headache—in the short-term, but it’ll pass. If you’d rather avoid those symptoms, skip the coffee when you’re already thirsty, and have a glass of water.

Drinking the recommended amount of water is the easiest and most efficient way to keep your body optimally hydrated. If you’re not a fan of regular water, you can add fresh fruit or drink sparkling water. You can also have low-sugar juice, caffeine-free tea, and fruits with a high water concentration, such as watermelon, citrus fruits, and strawberries. And there’s always tea. Dark tea, like lapsang souchong, can have a coffee-like taste and comparable energy-boosting properties with about half the amount of caffeine.

The bottom line: Don’t replace coffee with water

If you’re worried about becoming dehydrated from your daily cup of coffee, don’t fret. While the caffeine does have a diuretic effect, the drink won’t dehydrate you drastically. You should be mindful about the caffeine content of your coffee, as higher caffeine levels cause great diuretic effects. That said, you should still prioritize hydration and wellness. That means drinking water every chance you get and staying extra hydrated on hot days or when you’re exercising.

“The importance of proper hydration can’t be overstated, as water and chemical balance is crucial for maintaining overall health and well-being,” Dr. Cutler advises.