Does Coffee Dehydrate You? The Answer May Surprise You

Few things are as routine for the masses as drinking a cup of coffee in the morning. In fact, an estimated 154 million US adults over the age of 20 say they drink coffee, with nearly half of the population choosing to drink a cup of joe daily. It makes sense: Some days, it may feel like that little jolt of caffeine is essential to stay moving in a fast-paced world. 

Coffee offers some surprising benefits beyond the energy boost it provides, too. With moderate consumption, caffeine in coffee can improve memory, mood, reaction times, and mental function, according to the Cleveland Clinic. Coffee also contains nutrients like B vitamins, potassium, and riboflavin, as well as antioxidants that help prevent cell damage. It may even lower your risk of diseases like diabetes, cancer, and Parkinson’s. 

But what about the drawbacks associated with your daily cuppa? Can too much of a good thing have health implications like dehydration? We chatted with registered dietitians to find out.

Does Coffee Dehydrate You?

If you feel like you need a bathroom break shortly after drinking your java, it’s not your imagination—but in moderate amounts, coffee won’t lead to dehydration. “Coffee is a diuretic, meaning it increases urine production,” says Sarah Olszewski, RDN, a registered dietitian and nutrition advisor for Cure. “If the fluid lost through urine is not adequately replaced, it can result in dehydration—but the dehydrating effects of coffee depend on the amount you consume, your overall fluid intake, and individual tolerance to caffeine,” Olszewski explains. 

Generally, though, if you drink a moderate amount of coffee, you don’t need to worry about it affecting your H2O levels too much. A 2016 meta-analysis published in the Journal of Science and Medicine in Sport found that caffeine doesn’t lead to dehydration for healthy adults, and a 2014 study published in PLOS ONE suggests that moderate daily coffee intake doesn’t negatively impact your fluid balance (and may even contribute to your daily fluid requirement—more on that later!).

Caffeine’s Diuretic Effect, Explained

Caffeine, the active chemical in coffee, increases the production of urine. Because of that, coffee is considered a diuretic, something that stimulates the kidneys to produce more urine and leads to excess fluid losses, Olszewski says. However, this diuretic effect is mild per cup of coffee, says registered dietitian Maria Sorbara Mora, RD. A morning cup or two shouldn’t cause any havoc on your hydration levels.

“You would need to consume more than 500 milligrams of caffeine per day (that’s five cups of coffee!) to see a significant diuretic effect in the first place,” Mora says. What’s more, these cups would need to be consumed all at once for the body to increase urine production significantly enough to cause dehydration, she explains. 

Interestingly, ritual coffee drinkers also build a tolerance to the diuretic effect, meaning it becomes less of a diuretic for them and the caffeine won’t cause them to urinate as much as it does for those who don’t drink it regularly, Mora says. 

Does Coffee Count as Water Intake?

Considering coffee’s diuretic effect, it may seem contradictory, but your morning brew can contribute to your daily water intake, Olszewski says. “A cup of coffee is approximately 98 percent water on average,” she says. “And that amount is generally sufficient to offset the increased urine production caused by caffeine.”

Technically speaking, the amount of coffee (and all of its water content) is typically greater than the diuretic effect of caffeine. “For example, 300 milligrams of caffeine will cause the body to produce a little over 100 milliliters of urine,” Olszewski says. “So, yes, you can say some of the water in coffee can be used as part of your daily fluid intake.” 

That said, it’s wiser to consider it an even swap, especially since coffee comes in different strengths (and sizes), making it difficult to verify the checks and balances for your water intake. What’s more, caffeine can cause a laxative effect that can further impact hydration levels. “Evidence shows that coffee and caffeine increase the hormone cholecystokinin, which stimulates the colon, giving you the urge to go,” Mora says. “Drinking more than two or three cups of coffee per day can cause loose stool or diarrhea, and when you have severe diarrhea, your body loses substantial fluid.” 

If you want to have coffee count as some of your water intake, consider a half-caf or decaf roast, which makes the water-to-caffeine ratio even more significant, Mora suggests.

How Much Coffee Is Safe to Consume?

The amount of coffee that’s considered safe to consume can vary from person to person, depending on individual tolerance to caffeine and other factors. According to the Food & Drug Administration (FDA), moderate coffee consumption (which is considered safe for most adults), is 400 milligrams of caffeine daily, which equates to about four to five cups per day. “This level of consumption is not associated with an increased risk of major chronic diseases and is not likely to have adverse health effects for most individuals,” Olszewski says. But above this recommended amount, people have reported negative or even dangerous side effects, Mora says.

Remember, too, that not everyone can safely drink five cups of coffee on the daily. For example, the American College of Obstetricians and Gynecologists (ACOG) recommends that pregnant people limit caffeine consumption to less than 200 milligrams (about two cups) per day.

But even folks without certain health conditions should consider moderating their coffee consumption. “Some people are very sensitive to the effects of caffeine and individuals metabolize it at different speeds,” Mora explains. “It’s important to be aware of the side effects of drinking caffeine and cap it to where your body feels safe.” Some of these side effects include increased heart rate, insomnia, anxiety, headache, and gastrointestinal symptoms such as nausea and diarrhea. 

Finally, if you’re drinking large amounts of coffee on a regular basis, it’s wise to increase your overall water intake, Mora says.

How to Tell If You’re Dehydrated

Though it’s rare you’ll experience dehydration from drinking coffee, it’s important to practice body awareness while staying caffeinated and pay attention to any signals that may point to overconsumption. Remember: Coffee’s laxative effect can cause diarrhea, which is more likely to lead to dehydration than the act of drinking coffee itself. 

Here are some common dehydration symptoms to know, according to Mora: 

The Takeaway

Overall, it’s good news for coffee lovers: Experts say you can drink your morning cuppa without worry that it’ll impact your hydration levels in any meaningful way. Just don’t consume more than five cups in one sitting, and pay attention to what your own body is telling you about how it reacts to caffeine and its diuretic and laxative effects. The biggest concern is diarrhea; a severe case caused by drinking too much coffee can severely impact hydration levels. Otherwise, there’s no need to hit pause on your daily cup of joe.

This content is for informational and educational purposes only and does not constitute individualized advice. It is not intended to replace professional medical evaluation, diagnosis, or treatment. Seek the advice of your physician for questions you may have regarding your health or a medical condition. If you are having a medical emergency, call your physician or 911 immediately.