Dehydration occurs when the body loses more fluid than it takes in, disrupting metabolic processes and normal body functions. Lack of sufficient fluid intake during strenuous outdoor activities can result in dehydration. Thirst isn’t always a reliable early indicator of the body’s need for water. Many people don’t feel thirsty until they’re already dehydrated, underscoring the importance of increased water intake during hot weather.

Health Risks of Dehydration

Dehydration can lead to serious complications, including:

  • Heat injury. If adequate fluids are not consumed during physical exertion and heavy perspiration, heat injury may occur, ranging in severity from mild heat cramps to heat exhaustion or potentially life-threatening heatstroke.
  • Urinary and kidney problems. Prolonged and repeated bouts of dehydration can cause urinary tract infections, kidney stones, and even kidney failure.
  • Seizures. Electrolytes – such as potassium and sodium – help carry electrical signals from cell to cell. When electrolytes are out of balance, the normal electrical messages can become mixed up, leading to involuntary muscle contractions and sometimes to a loss of consciousness.

Mild/Moderate Dehydration Symptoms

  • Extreme thirst
  • Less frequent urination
  • Dark-colored urine
  • Fatigue
  • Dizziness
  • Confusion
  • Headache
  • Dryness of skin, mouth, and eyes

First Aid

  • Mild/moderate dehydration can be treated by stopping activity, getting the worker to a cool/shaded area, and drinking fluids (water or electrolyte containing sports drinks).
  • Seek immediate medical attention if the worker faints or losses consciousness, has heart palpitations or rapid heartbeat, or a fever.

Dehydration Prevention

Increase fluid intake during:
  • Strenuous activity. Start hydrating at least a day before strenuous activity. During activity, replenish fluids at regular intervals and continue drinking water or other fluids afterward.
    • Drink 1 cup of water every 15 - 20 minutes (about 24 - 32 fl oz per hour).
    • Do not drink more than 48 fl oz per hour. Too much water or fluids can cause low sodium levels in the blood resulting in hyponatremia, a medical emergency.
  • Hot and humid conditions increase your risk of dehydration and heat illness. Humid air causes sweat to evaporate more slowly preventing the body from cooling itself, leading to increased body temperature. More fluid intake is required during work in the heat to replace moisture loss from sweating.
  • During cold weather, drink extra water to combat moisture loss from dry air, particularly at higher altitudes.
What to Drink:
  • Water. Adequate water intake and eating regular meals are typically sufficient to maintain hydration and electrolyte balance during work in the heat.
  • Sports drinks. For prolonged sweating lasting several hours, sports drinks with balanced electrolytes can replace salt lost in sweat.
What to Avoid:
  • Energy Drinks. High caffeine levels can affect your heart and can be risky when added to the strain placed on your body by heat.
  • Alcohol. Drinking alcohol within 24 hours of working in the heat can increase the risk of dehydration and heat illness.
  • Salt tablets. The National Institute for Occupational Safety and Health (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.


  1. CDC-NIOSH – Heat Stress – Dehydration Flyer:
  2. CDC – Rehydration Therapy:
  3. Cleveland Clinic – Dehydration:
  4. Mayo Clinic – Dehydration:
  5. Mayo Clinic – Hyponatremia:
  6. UMD Dehydration Fact Sheet:
Last Updated: 5/16/2023