During my years as a Nutritional Therapist one question comes up time and time again and that is ‘do coffee and tea make you dehydrated?’

Well, as with all things dietary there is no definitive answer to this but here is some information that may help to explain what happens in the body when you drink beverages containing caffeine:

Both coffee and tea (and many soft drinks) contain caffeine which is a diuretic – a substance that increases urinary output through the kidneys.

I think it has always been a perceived wisdom that drinking several cups of tea or coffee and day will increase the need to pee and therefore cause dehydration. However there is little evidence to support this theory. It is unlikely that the fluid loss will be in excess of the volume ingested when taking a drink that contains caffeine.

A recent study found that in doses over 360mg caffeine does have a diuretic effect – the average cup of coffee (8 fl oz or just over 200ml) contains approximately 95mg of caffeine. However it appears that regular drinkers will build up a tolerance to caffeine therefore making it less likely to increase the need to go to the loo.

A 2014 study found that men who drank four 200ml cups of coffee a day were no more likely to urinate more than those who were drinking the equivalent amount of water.

When considering the caffeine in energy drinks, research has found that they can increase urinary output but the subjects of the research were already in a state of dehydration.

Why does coffee make me want to pee?

If you are already in a hydrated state then drinking a large coffee – 12 fl oz – will probably mean that you will pee out a similar amount of urine afterwards.

For some consumers caffeine can cause bladder incontinence – when you feel the urge to pee more urgently and frequently. This can also be exacerbated by alcohol and some medications. In this instance it’s very important to keep hydrated because concentrated urine can irritate the bladder lining so it may be sensible to monitor your caffeine consumption.

Possible side effects

It’s worth noting there are also other side effects associated with caffeinated drinks, which include:

  • rapid heart beat (palpitations)
  • restlessness and excitability
  • anxiety and irritability
  • trembling hands
  • sleeplessness


The bottom line

If you think you are sensitive to caffeine then make sure you are drinking water at the same time (in Europe you will frequently be given a small glass of water alongside your coffee).

  • Avoid drinking caffeinated drinks near bedtime to avoid having to get up during the night.
  • Be aware of other drinks and over the counter medications that may contain caffeine especially energy drinks and flu remedies.
  • Drinking 6-8 glasses a day of plain water will help you to stay hydrated and drink more if you are exercising.
  • Look at your pee – it should be straw coloured throughout the day. Be aware that supplements containing Vitamin B2 (riboflavin) can make the pee appear a bright yellow.



image courtesy of www.freedigitalphotos.net (photographer: punsayaporn)