Sweating cools the body but also causes
dehydration. Sweat that evaporates from the skin is
more effective at cooling than sweat that drips off the body.
Drinking while you exercise does not replace all of the water lost in
sweat quickly enough. Be sure to increase your fluid intake before you
exercise and continue to drink after you finish exercising in hot weather. It
is easy to become dehydrated during exercise, which increases the risk for a
You can help prevent dehydration and a
heat-related illness. Drink plenty of water before, during, and after you are
active. This is very important when it's hot out and when you do intense
Drink on schedule. Two hours before exercising,
drink 24 fl oz (750 mL) of
fluid. Drink 16 fl oz (500 mL)
of fluid 15 minutes before exercising. Continue drinking
8 fl oz (250 mL) of fluid every
15 minutes while exercising.
Drink rehydration drinks which are absorbed
as quickly as water but also replace sugar, sodium, and other nutrients. Eat
fruits and vegetables to replace nutrients.
Watch your weight
while exercising. Drink
16 fl oz (500 mL) for every
1 lb (0.5 kg)
Check your urine. Urine should be clear to pale yellow, and
there should be a large amount if you are drinking adequately. You should
urinate every 2 to 4 hours during an activity when you are staying properly
hydrated. If your urine output decreases, drink more fluids.
not spend much time in the sun. If possible, exercise or work outside during
the cooler times of the day. Wear lightweight, light-colored, loose-fitting
clothing in hot weather, so your skin can cool through evaporation. Wear a
wide-brimmed hat or use an umbrella for shade.
Stay cool when
possible. Take frequent breaks in the shade, by a fan, or in air-conditioning.
Cool your skin by spraying water over your body. Take a cool bath or shower 1
to 2 times a day in hot weather.
Do not drink caffeine or
alcohol—they increase blood flow to the skin and increase your risk of
Do not use salt tablets, which are
absorbed slowly and can cause irritation of the stomach. Salt tablets do not
replace water loss.
Primary Medical Reviewer
William H. Blahd, Jr., MD, FACEP - Emergency Medicine
How this information was developed to help you make better health decisions.