How much water should you actually drink in a day?

Updated Feb 5, 2025 | 11:00 PM IST

How Much Water Should You Drink?

SummaryAs per experts, drinking 8 glasses of water a day may be unnecessary and the research estimates that the actual requirement is around 1.5 to 1.8 liters per day. This not only includes water, but all kinds of fluids from all sources that we may consume in a day.

We all know that drinking water is good for us. If you are feeling tired, have some water. Have a dry skin? Have some water. Have a dry throat? Have some water. It is almost like water is the fix to all our issues. May be it is, but not always. So, are we sometimes drinking more water than necessary? What happens then?

Many say that there is an 8x8 rule one must follow when it comes to drinking water.

What is the 8x8 drinking water rule?

Many believe that in the 8x8 rule, eight 240ml glasses of water per day adds up to almost 2 liters. However, it is not in the guidelines in both the UK and the EU health advisory. None of them recommends this specific amount.

So, where did it origin from?

The origins of this rule seem to come from misinterpreted advice given decades ago. In 1945, a US advisory board suggested adults should consume one milliliter of fluid per calorie of food, totaling about two liters for women and 2.5 liters for men. Importantly, this included all drinks and even water-rich foods like fruits and vegetables.

A later book in 1974 recommended six to eight glasses of water daily but also noted that coffee, tea, and even beer could count towards hydration. Yet, the idea of drinking two liters of plain water daily took hold and has persisted ever since.

How Much Water Do We Really Need?

As per experts, drinking 8 glasses of water a day may be unnecessary and the research estimates that the actual requirement is around 1.5 to 1.8 liters per day. This not only includes water, but all kinds of fluids from all sources that we may consume in a day.

Also, studies show that instead of following a rigid routine, what is best is to focus on factors like temperature, physical activity and health conditions for your water intake. Those in hot and humid climate, high altitudes or pregnant or breastfeeding, and athletes may require more water. Whereas those in cooler areas, with a more sedentary lifestyle won't. However, for the average person, thirst is a more reliable guide than any fixed rule.

ALSO READ: What Happens When You Drink Too Much Water?

Science of Hydration and Dangers Of Over hydration:

Water is necessary to transport nutrients, control temperature, and keep organs functioning. We lose water through sweat, urine, and respiration, so staying hydrated is critical. However, dehydration develops only when the body loses 1-2% of its total water content.

A widespread myth is that feeling thirsty indicates that you are already severely dehydrated. Experts argue that thirst is an excellent evolutionary mechanism that ensures us drink when we need to. The body also produces hormones that aid in water conservation when necessary.

Drinking More Water Than Needed:

While drinking too much water is generally harmless, it can cause hyponatremia, a condition in which salt levels in the blood become dangerously low. This can result in brain enlargement, disorientation, convulsions, and, in extreme cases, death.

There have been reports of athletes overhydrating during endurance races, resulting in significant difficulties. Experts caution that simply following hydration myths might be dangerous, stating that thirst remains the greatest signal of when to drink.

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