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Heat Stress: Hydration

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Drinking enough fluids is critical for preventing heat illness. It takes discipline to drink adequate fluids while working in the heat, but it is one of the most important ways to keep yourself safe.

 Vertial arrow with color changing from clear to dark yellow from top to bottom. Labels indicating level of hydration are placed along the arrow, with a darker color corresponding with increased dehydration.

Hydrate Before Work

•  Being hydrated when you start work makes it easier to stay hydrated through the day.

•  If you are dehydrated when you start work, you may not be able to drink enough to catch up with your body’s need for water.

Hydrate During Work

•  Drink before feeling thirsty. By the time you feel thirsty, you are already behind in fluid replacement. Dehydration is a primary contributor to heat exhaustion.

•  Your work performance may suffer when you are dehydrated, even if you don’t notice.

• When working in the heat, drink 1 cup (8 ounces) of water every 15–20 minutes.

Graphic showing the same volume of liquid in different measuring units and containers: a full quart container, a full liter container, and a one-fourth full gallon container

        • This translates to ¾ – 1 quart per hour.

        • Drinking at shorter intervals is more effective than drinking large amounts infrequently.

•  Do not drink more than 48 oz (1½ quarts) per hour! The goal is to replace fluids lost in sweat, not to overload yourself with extra fluids. Drinking too much water or other fluids (sports drinks, energy drinks, etc.) can cause a medical emergency because the concentration of salt in the blood becomes too low.

Hydrate After Work

•  Most people need several hours to drink enough fluids to replace what they have lost through sweat. The sooner you get started, the less strain you place on your body from dehydration.

•  Hydrating after work is even more important if you work in the heat on a regular basis. Chronic dehydration increases the risk for a number of medical conditions, such as kidney stones.

  

What to Drink

bottled water beside glass of waterWater

Water will almost always maintain
hydration during work in the heat,
as long as you eat regular meals
to replace salt lost in sweat.

 

What to Avoid

Energy Drinks
  • Some energy drinks contain much more caffeine than standard servings of coffee, tea, or soft drinks.
  • Drinking several energy drinks per day can raise your caffeine levels enough to affect your heart. High caffeine levels can be risky when added to the strain placed on your body by heat.
  • Many energy drinks contain as much or more sugar as soft drinks, which adds hundreds of extra calories to your diet.
Alcohol
  • Alcohol can cause dehydration.
  • Drinking alcohol within 24 hours of working in the heat can increase the risk of heat illness.

 

Additional Information

What about salt tablets?
  • NIOSH does not recommend taking salt tablets.
  • In most cases, salt can be replaced by eating normal meals and snacks throughout the day. Do not skip meals.
What about caffeine?
  • The amount of caffeine in tea, coffee, and soft drinks probably will not have an effect on overall hydration, unless these beverages are consumed in large quantities.
Do I need sports drinks?
  • In general, eating regular meals with adequate water intake is sufficient to maintain water and electrolyte balance.
  • For prolonged sweating lasting several hours, sports drinks with balanced electrolytes are another option to replace salt lost in sweat.
  • Heavy consumption of sports drinks will add unnecessary calories to your diet due to the added sugar.

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