Hydration

Should You Drink Water With Coffee? Why Coffee Is Served With Water

Should you drink water with coffee? Not for hydration, but it's still a smart habit. Why coffee is served with water, and when a glass helps most.

By the Caffeine vs Water team · 28 September 2026 · 7 min read

In a good café, your espresso often comes with a small glass of water. Some apps and fitness blogs go further and tell you to drink water with coffee, a glass for every cup, to "make up for" it. Should you? The honest answer is that you don't need to for hydration, but the habit is worth keeping, for different reasons than the ones you usually hear.

Do you need to drink water with coffee to stay hydrated?

No. Caffeine is a mild diuretic, which is where the "coffee dehydrates you" idea came from. But a cup of coffee is mostly water, and regular coffee drinkers develop a tolerance to caffeine's effect on the kidneys.

The best test of this is a 2014 study from the University of Birmingham. Fifty men who normally drank 3–6 cups a day spent three days drinking four 200 ml cups of coffee and three days drinking the same amount of water. Total body water, blood markers and 24-hour urine volume were the same on both. The authors concluded moderate coffee "provides similar hydrating qualities to water".

A 2016 study of 13 drinks backed this up: coffee and tea were retained just as well as still water over 4 hours. So your coffee counts toward your daily fluids, and the U.S. National Academies includes caffeinated drinks in its water guidance. It doesn't subtract from them. The full evidence is in does coffee dehydrate you?, and what counts as water intake covers tea, milk and sparkling water.

When a glass of water with coffee helps

1. After a very strong coffee

Dose matters. In a 2017 study, regular coffee drinkers had coffee with either about 269 mg or 537 mg of caffeine. The lower dose didn't change fluid balance. The higher one, around 6 mg per kg of body weight, nearly doubled urine output over the next 3 hours (613 ml versus 356 ml after water). A 2015 meta-analysis found caffeine raised urine volume by about 109 ml on average, mostly at rest; the effect largely disappeared during exercise.

Most single drinks are nowhere near 537 mg. But a venti cold brew, a large drip coffee or an energy drink can get into the few-hundred-milligram range, and stacking them brings you closer.

2. It slows down the next refill

This is the most useful reason. A glass of water between coffees puts time and a bit of fullness between you and the next cup. It's easy to reach for another coffee when you're really just thirsty, or want something to hold. Water answers that without adding caffeine that will still be in you at bedtime.

3. It keeps water on your radar

Coffee is the one drink most people never forget. Tying water to it links a new habit to one you already have, which is how habits stick. If you have three coffees a day, that's three reminders to drink water.

4. It clears your palate

For flavour, water before coffee, especially espresso, rinses away whatever you last ate or drank, so you taste the coffee rather than your breakfast. A sip after clears the bitterness.

Why is coffee served with water?

The glass of water that comes with an espresso or a Viennese coffee is a café tradition. It's usually traced to the coffee houses of Vienna, and it spread to Italian espresso bars. Today, the reasons baristas give are practical:

• To clean your palate before the espresso, so the first sip tastes of coffee and nothing else.
• To rinse away bitterness after, especially with a strong or dark roast.

Some cafés serve sparkling water, which many people find more refreshing as a palate cleanser. It hydrates exactly like still water. Hydration was never really the point of the tradition, though. It's about taste.

Which coffees are worth pairing with water?

A simple rule: pair a glass with anything strong or concentrated. Here's how common drinks compare, using the caffeine values in our drink catalog. In Caffeine vs Water, drinks marked "Yes" add a paired glass of water to your goal.

Milky drinks like a latte or cappuccino already bring plenty of fluid, and milk was one of the most hydrating drinks in the 2016 study. The glass matters most with espresso shots and big filter or cold brew coffees. For more on how shot-based drinks compare with filter coffee, see espresso vs drip coffee.

Should you drink water before or after coffee?

Either works, and the best time depends on what you want from it:

• Before: better for taste, since it clears your palate. A glass first thing in the morning, before your first coffee, is also an easy way to start the day's water.
• After: better for pacing. A glass after your coffee delays the urge for another.
• Alongside: the café way, sipping between mouthfuls. Fine for both.

There's no evidence that the timing changes how your body handles the caffeine.

Does water flush out caffeine?

No. This is the one thing a glass of water can't do. Your liver breaks down caffeine, mainly with an enzyme called CYP1A2, and it works at its own pace. Drinking more water makes you pee more water, not more caffeine, and it doesn't shorten caffeine's half-life of around 5 hours.

So if you've had a 4 pm cold brew and you're worried about sleep, water won't fix it. What helps is the dose and timing of the next drink: a smaller cup, an earlier cutoff or a decaf. The bedtime caffeine calculator shows how much will still be active when you go to bed, and how long caffeine lasts explains why it varies so much between people.

Do you need a glass for every cup?

You don't need a strict one-for-one rule. With regular coffee, the coffee itself already counts as fluid. The glass matters more with strong drinks and when you're drinking several a day. That's the approach we built into Caffeine vs Water: a strong coffee adds one glass to your water goal, capped for the day, and normal cups simply count as fluid. It's a habit, not a correction.

If you find yourself relying on water to "balance out" a lot of coffee, it may be the coffee that's worth looking at. How to cut back on caffeine has a gentle taper plan.

Sources

1. Killer SC, Blannin AK, Jeukendrup AE. No evidence of dehydration with moderate daily coffee intake. PLoS One, 2014.
2. Seal AD, et al. Coffee with high but not low caffeine content augments fluid and electrolyte excretion at rest. Front Nutr, 2017.
3. Zhang Y, et al. Caffeine and diuresis during rest and exercise: a meta-analysis. J Sci Med Sport, 2015.
4. Maughan RJ, et al. A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index. Am J Clin Nutr, 2016.
5. Evans J, et al. Caffeine. StatPearls, NCBI Bookshelf.
6. National Academies. Report sets dietary intake levels for water, salt, and potassium, 2004.

General wellness information, not medical advice. If you're pregnant, have a heart condition, or take medication that affects caffeine, check your limits with a doctor.