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 caffeine and hydration. 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 about caffeinated water?
  • Is caffeinated water better than energy drinks?
  • Why does coffee make you pee?
  • How does caffeine affect urine output?

In This Series:

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

Short on time? This blog post is available in podcast form! The Caffeine at Midnight Podcast is available wherever you get your podcasts.

Are you really peeing more? How does caffeine affect urine output?

First of all, people who DO normally consume caffeine won’t feel an increase in the urge to go or an increase in urine output unless they’ve abstained from caffeine for at least one week. Secondly, for people who don’t consume caffeine regularly, doses of 250 mg caffeine or more increase urine output. In fact, for caffeine consumers and non-caffeine consumers alike, there’s no increase in urine output unless you drink MORE THAN 250 mg caffeine.

In summary, you only have an increase in urine output when you have more than 250 mg caffeine. Furthermore, 200 mg caffeine is the recommended max for caffeine-per-serving, according to the European Food Safety Authority. As a result, if you abide by that 200 mg caffeine recommendation, you won’t have to worry about increased bathroom breaks!

Why does coffee make you pee?

A diuretic is something that increases urine output. Even though caffeine is considered a diuretic, it does not increase the kidney glomerular filtration rate. In other words, caffeine does not increase the speed your kidneys filter your blood. On the contrary, caffeine inhibits sodium reabsorption in the proximal tubule.

In conclusion, if you absorb less sodium, your urine feels more salty and concentrated. Therefore, you feel more compelled to go to the bathroom.

Is it safe to drink caffeine on a hot day? Doesn’t caffeine make you dehydrated?

In fact, caffeine’s diuretic effect disappears when you’re working out because exercise stimulates catecholamines. Catecholamines counteract caffeine’s diuretic effect. For this reason, whether you’re sweating because you’re working out or because it’s a hot day, caffeine loses its diuretic effect.

Why are women more sensitive to caffeine?

Caffeine modifies the CYP1A2 activity and females have different CYP1A2 activities than males. As a result, women are more susceptible to the caffeine diuretic effect because of enzyme activity that differs between men and women.

Can all caffeinated drinks hydrate you the same as water?

Black Tea versus Water: No difference.

Research studies found no difference in urine output between black tea and water

Coffee versus Water: No difference.

Research studies found no difference in urine output or total body water measurements between coffee and water

Caffeine-free Soda versus Caffeinated Soda:

First of all, this research study didn’t compare soda to water, only soda with and without caffeine. Second of all, there was no difference in saliva production between caffeinated soda and decaffeinated soda. Finally, because of the carbonation, water is a better choice for hydration than soda

Read This Next: A Review of Select Caffeinated Waters


  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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