28/04/2026
COFFEE IS OUR FRIEND!! Also, science blah blah COFFEE good. I feel so seen 😂😂😂
No, coffee doesn’t dehydrate you.
If you drink 16 oz of coffee, that 16 oz is (almost) as hydrating as 16 oz of water.
In a 2016 randomized controlled trial,[PMID:26702122] participants consumed one liter of water and three of the following test drinks in a randomized order: sparkling water, Coke, Diet Coke, Powerade, orange juice, an oral rehydration solution, beer, hot black coffee, hot black tea, cold black tea, full-fat milk, or skim milk. They collected participants’ urine for 4 hours after ingestion to assess differences in urine output among beverages (less urine output = greater hydration).
One liter of coffee produced roughly the same urine output as one liter of water. Urine output was lower than water when participants drank an oral rehydration solution (as expected), full-fat milk, and skim milk, suggesting these beverages are more favorable for water than hydration.
Other research supports these findings. In 2014, researchers gave 50 habitual coffee drinkers 3-6 cups/day of coffee or water and observed their hydration status over three days. There were no differences in total body water, urine volume, urine specific gravity, or urine osmolality; the only difference was increased sodium excretion in the coffee group.[PMID:24416202] A 2015 meta-analysis looked at the impact of caffeine on urine production - the effect size was very small, with a lot of variation between studies. And exercise negated the small diuretic effect of caffeine.[PMID:25154702]
While I don’t advocate replacing all your water intake with coffee (you’ll p**p a lot if you do), coffee does have a net hydrating effect.
