Heat exhaustion – symptoms, causes, risk factors and complications

heat exhaustion

This is a condition in which symptoms are including a rapid pulse and heavy sweating which are results of your body overheating. This is one of 3 heat – related syndromes where the heat cramps are being the mildest and heatstroke is being more severe. There are many causes for heat exhaustion such as high temperatures particularly combined with strenuous physical activity and high humidity [1]. If you do not get the right treatment, then the heat exhaustion can lead to heatstroke which is a life threatening condition. There are many people who do not know that the heat exhaustion is preventable condition so talk with your doctor how you can prevent it.

Heat exhaustion signs and symptoms

The signs and symptoms of the heat exhaustion can develop suddenly or over time, especially with prolonged periods of exercise. Here are possible signs and symptoms of the heat exhaustion [2]:

  • Headache
  • Nausea
  • Muscle cramps
  • Low blood pressure upon standing
  • Weak, rapid pulse
  • Fatigue
  • Dizziness
  • Faintness
  • Heavy sweating
  • Cool, moist skin with goose bumps when in the heat

If you have these symptoms and you notice that they have worsen or they do not improve within one hour, then talk with your doctor as soon as possible.

heat exhaustion

Heat exhaustion causes

The heat of your body with the environmental heat is resulting in core temperature – this is the internal temperature of your body. We know that our body need to regulate the heat gain (and heat loss which is happening in the cold weather) from the environment to maintain the body’s temperature which is normal, approximately 37 C (98.6 F). Here are the most common causes for heat exhaustion:

  • Your body’s failure to cool itself: When the weather is hot, then your body cools itself mainly by sweating. The evaporation of sweat is regulating your body temperature. But when you are exercising strenuously or otherwise you overexert in hot and humid weather, then your body is less able to cool itself efficiently. As a result of this, your body can develop heat cramp which is the mildest form of the heat – related illness. The signs and symptoms of heat cramps are usually including muscle cramps, thirst, fatigue and heavy sweating. You should have the right treatment because this can prevent heat cramps from progression to heat exhaustion. Heat cramps are usually treated by resting, getting into cooler temperature, such as shaded place or air – conditioned place and drinking fluids or sport drinks which have electrolytes (Powerade, Gatorade and others). [3]
  • Other causes: Not just the strenuous activity and hot weather can be causes for heat exhaustion, but also there are other factors that could lead to it such as
  • Overdressing: Particularly when you are dressed in clothes which do not allow your sweat to evaporate easily. [4]
  • Alcohol use: When you are drinking alcohol, then it can affect the ability of your body to regulate your temperature. [5]
  • Dehydration: This can reduce the ability of your body to sweat and maintain a normal temperature. [6]

Risk factors: Every single person can develop heat exhaustion but there are some factors which can increase your sensitivity to heat, such as:

  • Obesity: If you have extra weight, then it can affect your body’s ability to regulate its temperature and it can cause your body to retain more heat. [7]
  • Young age or old age: Infants and children which are younger than 4 and adults which are older than 65 have increased chances of heat exhaustion. [8]
  • Sudden temperature changes: People who are not used to heat are having increased chances of developing heat – related illness such as heat exhaustion.
  • Certain drugs: It is known that medications can affect the ability of your body to stay hydrated and respond appropriately to heat. Those medications are medications that are used to treat heart problems and high blood pressure (beta blockers, diuretics), reduce psychiatric symptoms such as delusions (antipsychotic) and reduce allergy symptoms (antihistamines). [9]

Complications: If you leave the heat exhaustion untreated, then it can lead to heatstroke which is a life – threatening condition and it is happening when your core body temperature reaches 400 C (104 F) or higher. If you have a heat stroke, then it needs immediate medical attention because this can help to prevent the damage to your brain and other vital organs which can result in death.


[1] Nichols AW. Heat-related illness in sports and exercise. Current Reviews in Musculoskeletal Medicine. 2014;7(4):355–65.

[2] Glazer JL. Management of heatstroke and heat exhaustion. American Family Physician. 2005;71(11):2133-40.

[3] Cheshire WP. Thermoregulatory disorders and illness related to heat and cold stress. Autonomic Neuroscience. 2016;196:91-104.

[4] Ely BR, Blanchard LA, Steele JR, et al. Physiological responses to overdressing and exercise-heat stress in trained runners. Medicine & Science in Sports & Exercise. 2018;50(6):1285-96.

[5] Yoda T, Crawshaw LI, Nakamura M, et al. Effects of alcohol on thermoregulation during mild heat exposure in humans. Alcohol. 2005;36(3):195-200.

[6] Akerman AP, Tipton M, Minson CT, Cotter JD. Heat stress and dehydration in adapting for performance: Good, bad, both, or neither?. Temperature (Austin). 2016;3(3):412–36.

[7] Dehghan H, Mortazavi SB, Jafari MJ, Maracy MR. Cardiac strain between normal weight and overweight workers in hot/humid weather in the Persian gulf. International Journal of Preventive Medicine. 2013;4(10):1147–53.

[8] Kenny GP, Yardley J, Brown C, et al. Heat stress in older individuals and patients with common chronic diseases. CMAJ. 2010;182(10):1053–60.

[9] Liu SY, Song JC, Mao HD, et al. Expert consensus on the diagnosis and treatment of heat stroke in China. Military Medical Research. 2020.


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