What Is Heat Exhaustion


Heat exhaustion results when your body overheats and cannot cool itself off. Exercise  or other physical activity can cause your body to overheat, especially in warm, humid weather. Your body loses fluids through sweat as you exercise. You risk dehydration if you don't replenish those fluids with water or other beverages. Dehydration increases your vulnerability to heat exhaustion. All people are susceptible to a range of heat-related disorders, including heat exhaustion. However, because of their weakened capacity to expel heat, children, older adults, and those with chronic illnesses are especially at risk. If untreated, symptoms may progress to heatstroke, a serious emergency that poses a threat to life.1 Exercise should be stopped, and exposure to radiative heat sources should be minimised, to prevent heat exhaustion. To promote heat dissipation, the person should be urged to drink cool liquids and take off or relax garments. More active cooling techniques to lower core temperature should be used in more severe circumstances. By raising public knowledge of the dangers of exposure to high temperatures and protracted exertion, heat-related disorders like heat exhaustion can be avoided.2

Causes of heat exhaustion

Typically, sweat serves as a natural air conditioner for your body, cooling your skin while it does so. Your body works incredibly hard to control its internal temperature when exercising (especially in warm weather). When your body’s temperature gets too high, and it is unable to lower it on its own, heat exhaustion results.

Your body loses water and electrolytes through sweat while you exercise. Minerals called electrolytes, such as sodium and potassium, are essential for your body to function correctly. You become dehydrated if your body loses excessive fluid and sodium (salt) without replacement. Heat exhaustion can result from dehydration.3

Other causes

  • Dehydration lowers the capacity of your body to sweat and maintains an average body temperature.
  • Alcohol consumption might interfere with your body’s ability to control your temperature.
  • Overdressing, especially when wearing clothing prevents sweat from quickly evaporating. 

Risk factor

  • Young age or old- Adults over 65 and infants and children under 4 are particularly vulnerable to heat exhaustion. In young people, the body’s capacity to control its temperature isn’t fully developed, and in older persons, It may be hampered by disease, medicine, or other causes
  • Few medications - Medications used to treat high blood pressure, heart issue, allergies, anxiety, or psychiatric symptoms like delusion can all impact your body’s capacity to stay hydrated and react to heat appropriately. These medications include beta-blockers, diuretics, tranquilisers, and drugs used to treat high blood pressure, allergies, and anxiety, and calm you down (antipsychotics). Furthermore, some illicit substances, like cocaine and amphetamines, might raise your body temperature
  • Obesity- Obesity can interfere with your body’s capacity to control its temperature, leading to increased heat retention
  • Sudden variation in temperature- If you are not adapted to heat, you are more prone to heat-related ailments, such as heat exhaustion. You run the risk of contracting a heat-related illness if you live in a region that has just experienced a heat wave, or travel to a warm climate from a cold one since your body hasn’t had time to adjust to the higher temperatures
  • Elevated heat index- The heat index is a single temperature rating that takes into account how you feel as well as the ambient temperature and humidity. High levels of humidity make you more susceptible to heat exhaustion and heatstroke since your sweat doesn’t evaporate as quickly and your body has a harder time cooling down. You should take efforts to stay cool when the heat index is 91 F (33 C) or above.4

Signs and symptoms of heat exhaustion

  • Heavy perspiration, skin turning pale and clammy, or developing a heat rash; nevertheless, on people with brown or black complexion , a change in skin tone may be more difficult to detect.
  • Fast, weak pulse
  • Nausea or vomiting
  • Muscle cramps
  • Tiredness or weakness 
  • Dizziness
  • Heat rash
  • Headache
  • Heat syncope
  • High temperature
  • Being very thirsty5

Management and treatment for heat exhaustion

Stabilisation  in a cool environment is the first step in treating heat exhaustion in patients. Patients may develop heatstroke if the cause of heat exhaustion is not promptly addressed. Wetting the skin can start evaporative cooling. Monitoring of the core temperature and electrolyte condition is necessary.

Transferring patients to the proper medical facility is advised in cases of severe dehydration, hyponatremic states, changes in mental status, or irritation of the central nervous system. The majority of moderate dehydration cases can be treated in the field using oral rehydration solutions containing salt. Medical professionals must be aware of the symptoms of hyponatremic heat exhaustion and refrain from giving hypotonic fluids (as regards sweat). Replacement of the lost sodium with ordinary saline should be done gradually. To avoid central pontine myelinolysis, serum sodium should be increased no faster than 2.5 mEq per L (2.5 mmol per L) per hour.6


  •  If you can, avoid the heat. If you must go outside, stay in the shade, especially between 11 a.m. and 3 p.m.
  • Keep away from exercise or other activities that increase body temperature.
  • Eat and drink cold things, and stay away from hot and alcoholic beverages.
  • Take a cool shower or splash cool water on your skin or clothing.
  • Make sure your home is cool. When it is dark, and the temperature outside has dropped, open the windows that were closed throughout that day.
  • If the temperature is below 35 degrees, electric fans can help. 
  • Check the temperature of the space, especially in areas where more vulnerable people  reside and sleep.
  • If you believe a hot house is harming your health or another person’s health, you can also request assistance from the environmental health office at your local council. They can check a rental property for health risks, sus as excessive heat.7


How common is heat exhaustion

Anyone can get heat exhaustion, but some factors make  you more sensitive to heat. Young or elderly age is one of them. Adults over 65 and infants and children under 4 are particularly vulnerable to heat exhaustion.

How is heat exhaustion diagnosed?

Medical professionals typically use a physical examination to identify heat exhaustion. Your healthcare professional will conduct an examination, take your temperature, and inquire about your most recent activities. Your doctor may request blood and urine tests if they suspect you may be suffering from heatstroke.

How can I prevent heat exhaustion?

Avoid overheating, drink fluids, stay safe in vehicles, time your activities, wear lightweight and loose clothes , wear sunscreen, and use ice packs.

When should I see a doctor?

You require emergency medical attention if the symptoms of heat exhaustion in you or your child don’t go away after roughly an hour of fluids and rest. 

Immediately seek assistance if you or someone you know:

  • Cannot keep fluids down or sip water.
  • Has a fever that is higher than 103 degrees F
  • Has difficulty speaking, getting up, or moving around.
  • Sweating heavily
  • Appears bewildered or passes out.


Heat exhaustion is a serious kind of heat illness. It can cause serious health issues and even death if left untreated. If you or your child exhibits symptoms of heat exhaustion, It is crucial to take a break in a cool location and consume lots of fluids. If symptoms persist after an hour or so, obtain medical help right away. Keep yourself hydrated, especially if you are exercising outside in the heat. If you feel weak or thirsty, pay attention to your body and take a break to let it rest.


  1. Heat exhaustion - an overview | sciencedirect topics [Internet]. [cited 2023 Jan 26]. Available from: https://www.sciencedirect.com/topics/nursing-and-health-professions/heat-exhaustion
  2. Kenny GP, Wilson TE, Flouris AD, Fujii N. Heat exhaustion. Handb Clin Neurol. 2018;157:505–29.
  3. Heat exhaustion: symptoms & treatment [Internet]. Cleveland Clinic. [cited 2023 Jan 26]. Available from: https://my.clevelandclinic.org/health/diseases/21480-heat-exhaustion
  4. Heat exhaustion - Symptoms and causes [Internet]. Mayo Clinic. [cited 2023 Jan 26]. Available from: https://www.mayoclinic.org/diseases-conditions/heat-exhaustion/symptoms-causes/syc-20373250
  5. Heat exhaustion and heatstroke [Internet]. nhs.uk. 2017 [cited 2023 Jan 26]. Available from: https://www.nhs.uk/conditions/heat-exhaustion-heatstroke/
  6. Glazer JL. Management of heatstroke and heat exhaustion. afp [Internet]. 2005 Jun 1 [cited 2023 Jan 26];71(11):2133–40. Available from: https://www.aafp.org/pubs/afp/issues/2005/0601/p2133.html
  7. Heatwave: how to cope in hot weather [Internet]. nhs.uk. 2022 [cited 2023 Jan 26]. Available from: https://www.nhs.uk/live-well/seasonal-health/heatwave-how-to-cope-in-hot-weather/
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Jaya Choudhary

Bachelor of Dental Surgery, MBA-HA, India

Jaya is a Dental surgeon with MBA in Hospital Administration. She has 2 years of
experience with exposure to both clinical and non-clinical work environments and a strong
passion for medical writing and educating the public about health and wellbeing.

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