Why Does Coffee Make You Pee

Why does coffee make you feel like you have to pee? Does caffeine make you dehydrated? What if it’s caffeine from tea? From an energy drink? This is the second in a three-part series on caffeinated water. In this series, we answer the most commonly asked questions including:

  • Does caffeine make you dehydrated?
  • If water makes you hydrated but caffeine makes you dehydrated, what does caffeine water do to your body?
  • Is caffeinated water better than energy drinks?
  • Does all caffeine make you dehydrated? Or just coffee?
  • How does caffeine affect urine output?

In This Series:

Caffeine, Urine Output, and Hydration – A Summary of the Science

Don’t have time to watch the full video? No worries! The key details are below.

Note – this episode contains some general scientific summaries but it also contains some pretty nerdy technical details about the kidney, glomerular filtration, and how females have different activity than males for cytochrome P450.

IF YOU ARE NOT INTO THE SUPER-NERDY SCIENCE, I’ve embedded some videos of my bulldog puppy playing at the beach and the park during all the super-sciency parts of my presentation. 

Does caffeine make you pee more? How does caffeine affect urine output?

  • For people who don’t consume caffeine regularly, doses of 250 mg caffeine or more increase urine output
  • For people who normally consume caffeine, caffeine will not increase urine output unless these caffeine drinkers have abstained from all caffeine for at least one week
  • Caffeine consumers and non-caffeine consumers don’t have any increase in urine output when they drink less than 250 mg caffeine

It’s worth noting this amount that increases urine output is higher than the amount of caffeine adults are supposed to have in one serving (200 mg caffeine is the limit per serving; 400 mg caffeine is the limit per day, according to the EFSA).

Why does coffee make you pee? What is caffeine’s diuretic mechanism?

  • A diuretic is something that increases urine output
  • Caffeine does not increase the kidney glomerular filtration rate
  • The caffeine diuretic mechanism involves caffeine inhibiting the sodium reabsorption in the proximal tubule
  • If you absorb less sodium, your urine feels more concentrated which means you feel more compelled to go to the bathroom

Is it safe to drink caffeine on a hot day? Does caffeine make you dehydrated?

  • Caffeine’s diuretic effect disappears when you’re working out because exercise stimulates catecholamines which counteracts caffeine’s diuretic effect
  • Whether you’re sweating because you’re working out or because it’s a hot day, caffeine loses its diuretic effect
  • Women are more susceptible to caffeine’s diuretic effect

Why are women more sensitive to caffeine?

  • Caffeine modifies the CYP1A2 activity and females have different CYP1A2 activity than males
  • Women are more susceptible to the caffeine diuretic effect because of enzyme activity that differs between men and women

Does all caffeine make you dehydrated? Is caffeinated water better than an energy drink?

It does matter whether you drink water, caffeine-in-water, or caffeine plus water plus other ingredients.

  • Caffeine in black tea does not make you more dehydrated than water – there’s no difference in urine output
  • Caffeine in coffee does not make you more dehydrated than water – there’s no difference in urine output or total body water measurements
  • There’s no difference in saliva production between caffeinated soda and decaffeinated soda
  • A drink with caffeine and electrolytes is not as good for hydration as a similar drink with electrolytes alone

Now on to Part Three: My Favorite Caffeinated Waters

Love this info? Want to learn more?

I’ve researched the science and safety behind energy drinks and their ingredients since 2003. This book is the culmination of my research:


  1. Zhang Y, Coca A, Casa DJ, Antonio J, Green JM, Bishop PA. Caffeine and diuresis during rest and exercise: A meta-analysis. J Sci Med Sport. 2015 Sep;18(5):569-74. doi: 10.1016/j.jsams.2014.07.017. Epub 2014 Aug 9. Review. PubMed PMID: 25154702; PubMed Central PMCID: PMC4725310.
  2. Kingsley M, Penas-Ruiz C, Terry C, Russell M. Effects of carbohydrate-hydration strategies on glucose metabolism, sprint performance and hydration during a soccer match simulation in recreational players. J Sci Med Sport. 2014 Mar;17(2):239-43. doi: 10.1016/j.jsams.2013.04.010. Epub 2013 May 20. PubMed PMID: 23702257.
  3. Killer SC, Blannin AK, Jeukendrup AE. No evidence of dehydration with moderate daily coffee intake: a counterbalanced cross-over study in a free-living population. PLoS One. 2014 Jan 9;9(1):e84154. doi: 10.1371/journal.pone.0084154. eCollection 2014. PubMed PMID: 24416202; PubMed Central PMCID: PMC3886980.
  4. Hildebrandt GH, Tantbirojn D, Augustson DG, Guo H. Effect of Caffeinated Soft Drinks on Salivary Flow. J Caffeine Res. 2013 Sep;3(3):138-142. PubMed PMID: 24761280; PubMed Central PMCID: PMC3777298.
  5. Ruxton CH, Hart VA. Black tea is not significantly different from water in the maintenance of normal hydration in human subjects: results from a randomised controlled trial. Br J Nutr. 2011 Aug;106(4):588-95. doi: 10.1017/S0007114511000456. Epub 2011 Mar 30. PubMed PMID: 21450118.
  6. Maughan RJ, Griffin J. Caffeine ingestion and fluid balance: a review. J Hum Nutr Diet. 2003 Dec;16(6):411-20. Review. PubMed PMID: 19774754.

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