Does Decaf Coffee Dehydrate You? The Truth About Decaf and Hydration

Decaf coffee’s the go-to for folks who love the flavour of coffee but want to skip the buzz. But does decaf still dry you out like its fully-caffeinated cousin? Let’s break the myth: Does decaf coffee dehydrate you? Short answer—no. And here's why.

Decaf coffee still delivers the comfort—without the caffeine crash.

Quick Answer: No, Decaf Doesn’t Dehydrate You

Decaf coffee contains only trace amounts of caffeine, typically around 2 to 7 mg per cup compared to 80–100 mg in a regular brew. According to the experts at Healthline, that tiny caffeine dose isn’t enough to have any real diuretic effect.

The idea that coffee dehydrates you comes from caffeine’s diuretic properties (i.e. making you pee more). However, studies show that moderate caffeine doesn’t lead to net fluid loss. In fact, this PLOS ONE study found that coffee hydrates you just as well as water when consumed in normal amounts.

Decaf has around 3 mg of caffeine. Regular? Closer to 95 mg. Big difference, same ritual.

Where the Myth Comes From

Caffeine can make you run to the loo more, especially in large quantities. But that doesn’t mean you’re losing hydration overall. As Mayo Clinic explains, your body still absorbs the water in the coffee. It balances out.

To see an actual dehydrating effect from caffeine, you'd have to drink a lot, like 5+ cups of strong coffee in a short period. But decaf doesn’t even come close. It’s got barely enough caffeine to register on the diuretic scale.

Is Decaf a Diuretic?

Technically? No. Decaf coffee is not considered a diuretic. According to Harvard Health, diuretic effects don’t kick in until you consume at least 300 mg of caffeine, which would mean drinking over 10 cups of decaf back to back. Highly unlikely.

So if you’re sipping a flat white made with decaf beans, you’re getting water, flavour, and antioxidants. Not a dehydration hit.

Even decaf deserves the bloom—it brings out that full-bodied richness.

What the Science Says

That PLOS ONE study we mentioned earlier tested hydration markers in people drinking coffee vs. water. Conclusion? There was no difference. The body uses both equally well for fluid replenishment.

Other findings back this up, too. A Healthline review confirms that caffeine-containing drinks like coffee and tea still count towards your fluid intake. Even the NHS agrees that tea and coffee can keep you hydrated as part of your daily water total—just don't overdo the sugar or syrups.

The Verdict

Does decaf coffee dehydrate you? Not even close. It's about 98% water and contains so little caffeine that its effect on your kidneys is practically nil. So yes, your morning mug of decaf counts towards your hydration, not against it.

Unless you’re chugging 10+ espressos, coffee (especially decaf) isn’t going to mess with your fluid levels. So keep sipping with confidence.

Decaf coffee hydrates almost as well as water—myth busted.

Ready for a Decaf That Tastes Like the Real Deal?

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Got questions about decaf or hydration myths? Drop a comment 💬