A surprising amount of myths and questions surround the topic of coffee and caffeine. “Does caffeine dehydrate you?” is actually something I get asked very often as a dietician. Today, we’ll take a look at the beliefs that lead to this question and at the facts that will debunk popular coffee myths!

Does caffeine dehydrate you?

Grab a hot cup of coffee and let’s dive into some popular myths and find out everything you need to know about your daily caffeine intake!


This is one of the many myths that surround the subject of hydration, but the reality is a little more complex. While it is true that caffeine has a diuretic effect, the quantity found in coffee and tea comes with a considerable amount of fluid. This usually leads to our body eliminating the same quantity of fluid that we took in.

Many of my clients are under the impression that coffee and tea do not count towards their daily fluid intake and tell me that they have trouble drinking two additional litres of liquid on top of their coffee.

I have good news for you: tea and coffee actually count as fluids! Even better: if you are drinking milk, eating yogurt or soup and eating fresh fruit and vegetables in the recommended daily amounts, these should account for about 20% of your daily fluid needs.

The average male should consume about 3 litres of fluids a day, while the average female’s liquid intake should be around 2.2 litres a day. For example, if you are an adult man and drink 1 litre worth of tea or coffee and get about 0.6 litres of water from the food you eat, that leaves you about 2 litres of other liquids to drink to fulfill your fluid needs on that day.

While drinking a cup of coffee or tea does not automatically cause dehydration, keeping track of our daily caffeine intake is still important. As a matter of fact, there are some studies that demonstrate that consuming more than 500 mg of caffeine a day (the amount found in 3-5 cups of coffee) can lead to a mild case of dehydration.

Drinking coffee doesn't usually cause dehydration, but keeping track of your caffeine intake is still important.


Health Canada publishes guidelines for caffeine intake. According to them, the average Canadian adult should consume a maximum of 400 mg of caffeine daily.

It is surprisingly easy to consume more than the recommended daily amount of caffeine, especially because a lot of guidelines tend to refer to the ideal number of cups of coffee someone should drink in a day.

Have you noticed how large coffee cups and mugs have gotten over the years? Some of them are two or three times larger than the cup of coffee nutritionists refer to!

Coffee cups have gotten larger over the years, making it easier to consume too much caffeine.

Most dietitians and nutrition experts recommend drinking a maximum of 3 cups of 250 ml of coffee or tea per day as an adult. This seems simple enough, but it can become tricky when the smallest cups of coffee in popular establishments exceed 250 ml!

To name a few, the smallest coffee you can get at Tim Hortons is 285 ml while at McDonald’s, it is 292 ml – nearly 17% larger than the recommended cup size!

To make caffeine tracking more complex, many of my clients often forget about other highly caffeinated products, such as soft drinks and chocolate. These can seem deceivingly inoffensive, but the average 355 ml cola drink contains an average of 35 mg of caffeine and in the case of Mountain Dew, a 355 ml can contain 55 mg, which isn’t a negligible amount.

This can become a problem because most of us tend to count on the invigorating effects of caffeine to give us enough energy to power through the day. Thankfully, there are plenty of other ways you can boost your energy levels with nutrition without relying on coffee!


With factors such as deceivingly large cups of coffee and the amount of caffeine in a cup of tea varying depending on how long it was steeped, it is important to know the signals your body sends you to let you know you are dehydrated.

Thirst is our body’s way to let us know we need to drink before becoming too dehydrated. This mechanism is pretty sensitive and will kick in if we are missing as little as 1% of the liquid we need. Other physical symptoms of mild dehydration include having difficulty concentrating, headaches, fatigue and lightheadedness.

If you are unsure as to whether or not you are dehydrated, pay attention to the colour of your urine. A pale colour indicates that you are well hydrated, while a darker colour means you need to drink some liquids.


Caffeine is a stimulant and it affects the nervous system. Some people will find that if they consume too much caffeine, they will feel nervous, they won’t sleep well or they will even experience some palpitations.  

Even though coffee, tea and cocoa can have a beneficial effect on your health, consume them in moderation.

Even though coffee, tea and cocoa contain plant chemicals that can have a beneficial effect on your health, it is important to consume them in moderation, especially if you are experiencing some mental health disorder symptoms as caffeine can amplify them. If that is the case, make sure to include some mood-boosting foods to your diet and to get plenty of rest and sleep daily.

I want to hear from you! Do you rely on coffee and caffeine to have enough energy to power through the day? Do you keep track of your daily caffeine intake? Let me know in the comment section below!