Should You Exercise If You Are Dehydrated?

Even mild to moderate dehydration can create potentially damaging consequences to your body during exercise. Not drinking enough fluids or losing too much bodily fluid causes dehydration. This ailment can thicken your blood, cause your blood vessels to narrow and increase your risk of developing blood clots, according to the National Institutes of Health. Exercising under these conditions is dangerous and can also prolong the effects of dehydration, causing even a mild case to increase in severity.

Man out of breath and sweating after working out.
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Exercising while dehydrated can produce significant consequences. Vigorous activity in hot or humid conditions above 80 degrees Fahrenheit can result in fluid losses greater than 1 liter per hour. Your body might lose more water than it can absorb, making it more difficult to stay hydrated the longer you exercise. Dehydration is also a cumulative process. You can become dehydrated with even a moderate exercise routine if you do not drink enough fluid to replace what you lose on a daily basis.


Dehydration occurs when fluid is lost in significant amounts from the body. As fluid is lost from the bloodstream and body tissues, an electrolyte imbalance occurs. Exercising under these conditions can have consequences ranging from mild heat cramps to potentially life-threatening heatstroke. Seizures can occur as a result of the electrolyte imbalance, causing involuntary muscle contractions and a potential loss of consciousness. Low blood volume can also cause hypovolemic shock, which creates a drop in blood pressure and significantly decreases the amount of oxygen available to the body, making exercise dangerous.


If you demonstrate any of the following symptoms, you should avoid working out until you have become properly hydrated. Symptoms of mild dehydration, which should still be monitored carefully, include a dry, sticky mouth, thirst, dry skin, headache, decreased urine, dizziness and constipation. If these symptoms are not properly treated, severe dehydration can occur. These symptoms include extreme thirst, little or no urination, rapid breathing, fever, extreme irritability and unconsciousness.


To prevent dehydration, drink an adequate amount of fluid several hours before exercise to allow the fluids to absorb into your tissues. While exercising, stay in cooler, shaded areas if possible and carry fluids with you at all times. Try working out during the early morning and late evening hours when the heat and humidity are at their lowest points. If your workout lasts longer than 45 minutes, consume a sports drink that contains sodium and potassium during the session. After working out, you should consume 24 oz. of water for every pound of body weight lost to properly rehydrate.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.
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