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Water: How much do I really need to drink?

Water is essential for life. You can only survive a few days without it. And being hydrated is essential for health. I could argue that water is the most essential nutrient of them all. Water is needed for every cell and function in your body.

So, water is critical for life and health.

But, just as way too little water is life-threatening, so is way too much. As with most things in health and wellness, there is a healthy balance to be reached.

But, there are conflicting opinions as to how much water to drink. Is there a magic number for everyone? What counts toward water intake?

Let’s dive right in.

Why is water so important?

Water plays several very important roles in the body. It works as a solvent, dissolving solids, liquids, or gases into chemicals that are then transported through water within the body where needed. It also serves as a catalyst for several intra-cellular metabolic reactions that would not take place otherwise.

Water is a huge part of your blood. It helps stabilize your blood pressure and heart beat. Body temperature control is regulated by water content and fluid balance thought sweating. Water also lubricates your joints and work as a shock absorber for the eyes and the spinal cord.

Lastly, water is a source of minerals for the body, such as calcium, magnesium, and fluoride, that are important for fluid balance between the intra- and extra-cellular environment, as well as in the blood.

And that's just a few of its roles.

How do I know if I need to drink more water?

You may not feel thirsty, but it does not mean that you are not dehydrated. If you experience any of these symptoms below, you might be chronically dehydrated:

- Increased thirst

- Dry mouth

- Tired or sleepy

- Decreased urine output

- Dark yellow urine

- Headache

- Fatigue

- Dry skin

- Dizziness

- Lethargy

- Soreness

- Heat exhaustion

Dehydration can impair mood and concentration, and contribute to headaches and dizziness. It can reduce your physical endurance, and increase the risk for kidney stones and constipation. Extreme dehydration can cause heat stroke.

If you have been under-hydrated for quite some time, your body's thirst signal (controlled by the pituitary gland through the antidiuretic hormone) might be under-regulated, and your kidneys are now functioning less optimally to remove toxins out of your body. Your blood, which is composed or water and the plasma (the solid component comprised of the red and white cells among others) must remain within a certain range to maintain vital functions. Similarly, the intracellular environment must contain a minimum percentage of water to perform optimally.

Therefore, under sub-optimal hydration status, the kidneys reduce water excretions and hence, the removal of toxins from the body is compromised to keep your water water status at the survival level.

How much water should I drink?

In the past, the recommendation was to drink eight-8 oz glasses, the “8x8 rule”, of water every day; that's about 2 liters of water. Over time, we've realized that imposing this "one size fits all" rule may not be the best approach.

Now, many health professionals recommend drinking according to thirst. You don’t need to go overboard forcing down glasses of water when you’re not thirsty. Just pay attention to your thirst mechanism. We have complex hormonal and neurological processes that are constantly monitoring how hydrated we are. And for healthy adults, this system is very reliable.

Besides thirst, which can become dysregulated as explained above, pay attention to how dark and concentrated your urine is. The darker your urine, the more effort your body is making to hold on to the water it has. Urine is still getting rid of the waste, but in a smaller volume of water, so it looks darker.

There are a few other things to consider when evaluating your hydration status. If you’re sweating a lot, or are in a hot/humid climate, drink more. Breastfeeding moms, elderly people, and people at risk of kidney stones need to drink more water too. So do people who experience episodes of vomiting and/or diarrhea, as both can quickly dehydrate our bodies.

So, ditch the “one size fits all” external rule, and pay more attention to your body’s subtle cues for water, that is thirst, fatigue, focus, and urine color.

But consider this: the bigger the person is, the more water he/she would need to circulate nutrients, lubricate joints and organs, regulate blood pressure, etc. Typically, we assume that a person needs to drink the equivalent of its body weight in kilograms in ounces of water. So if you weigh 150 lbs, that is 68kg, then you would need to drink 68 ounces of water, or 2 litres a day (there is 32 ounces per litre of water).

If you realize that you are not drinking enough water daily, you will need to make a conscious effort to reach your daily goal. If you barely drink any water, then you may want to increase your water intake by half a litre (4 oz) per day for a few days and then again until you reach the optimal water intake. At first, your kidneys will not be used to receive that flow of water, and will excrete a lot of this water. You will be in a euhydrated state (sufficiently hydrated) when you stop urinating too frequently.

What counts toward my water intake?

All fluids and foods containing water contribute to your daily needs.

Water is usually the best choice. If you're not drinking pure water, consider the effects that the other ingredients have on your body. Drinks containing sugar, alcohol, and caffeine will have effects besides hydration. Sugar can mess with your blood sugar balance. Alcohol can make you feel "buzzed." And caffeine can keep you awake.

Let's talk a bit more about caffeine for a second. Caffeine is the infamous "dehydrator," right? Well, not so much. If you take high dose caffeine pills, then sure, they cause fluid loss. But the idea that coffee and black tea don't count toward your water intake is an old myth. While caffeine may make you have to go to the bathroom more, that effect isn't strong enough to negate the hydrating effects of its water. Plus, if you're tolerant to it, that is regularly drinking it, then the effect is even smaller. So, you don’t need to counteract your daily cup(s) of coffee and/or tea.

Also, many foods contain significant amounts of water. Especially fruits and vegetables like cabbage, cantaloupe, watermelon, strawberries, celery, spinach, lettuce, apples, pears, oranges, grapes, carrots, and pineapple. These foods are over 80% water, so they are good sources of hydration.

So, you don’t need to count your plain water intake as your only source of hydration. All fluids and foods with water count.


There is no magic number of the amount of water you need, although you can base yourself on the idea of drinking half your bodyweight in water and adjust from there. Everyone is different. Children, pregnant women, and elderly need more. Episodes of vomiting or diarrhea will also increase your short-term need for more water. The most important thing is to pay attention to your thirst. Other signs you need more water are dark urine, sweating, constipation, and kidney stones.

Water is your best source of fluids. But other liquids, including caffeinated ones, help too. Just consider the effects the other ingredients have on your health as well. And many fruits and vegetables are over 80% water so don't forget about them.

Let me know in the comments: What’s your favourite way to hydrate?



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