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Do you ever wonder how much water or fluids you need each day to keep you hydrated, especially in the summer heat? Many of us grew up thinking we needed at least eight, 8-ounce glasses of water each day, or 64 ounces, to fulfill our daily fluid requirements. In reality, there really was no scientific evidence to support that recommendation but instead it was based on survey data of people’s usual consumption. Several studies and many years later, the recommendations for fluids have changed, but many of us are unaware of how much daily fluid intake we actually need to stay hydrated.

The truth is your water needs are dependent on many factors, including your age, health, medications you take, activity level and the climate in which you live but there are general recommendations you can follow.

Here are two common ways to calculate your water needs:

Dietary recommendations. The Institute of Medicine advises that healthy men consume roughly 3 liters (about 13 cups) of total beverages a day and healthy women consume 2.2 liters (about 9 cups) of total beverages a day.

Replacement approach. The average urine output for adults is about 1.5 liters (6.3 cups) a day. You lose close to an additional liter (about 4 cups) of water a day through breathing, sweating and bowel movements. Food usually accounts for 20% of your total fluid intake, so if you consume 2 liters of water or other beverages a day (a little more than 8 cups) along with your normal diet, you will typically replace your lost fluids.

In general, most experts agree that healthy adults may use thirst to determine their fluid needs. If you drink enough fluid so that you rarely feel thirsty and produce 1.5 liters (6.3 cups) or more of colorless or slightly yellow urine a day, your fluid intake is probably adequate. This month, pay attention to your thirst and track your fluid intake for at least one week to see if you are meeting the dietary guidelines for total fluid consumption.


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