Heatstroke and Heat Exhaustion: Symptoms, Causes, Risk Factors, and Prevention Tips | Max Hospital

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Heat Stroke and Heat Exhaustion: Differentiating the Symptoms and Severity

By Dr. Pankaj Chaudhary in Internal Medicine

Jun 21 , 2024 | 9 min read

This summer, with temperatures breaking all historic records, it has become more important than ever to protect yourself from the wrath of the summer heat. Two of the most common conditions resulting from excessive heat exposure are heat exhaustion and heatstroke. While both conditions share similar triggers, they differ significantly in severity and required interventions, and understanding these differences is crucial for effective prevention and timely treatment. To shed more light on the subject, in this article, we explore the symptoms, causes, and treatments of both of these potentially life-threatening situations.

What are Heatstroke and Heat Exhaustion?

Heat exhaustion

Heat exhaustion is a mild form of heat-related illness that typically occurs due to prolonged exposure to high temperatures combined with inadequate fluid intake. It serves as a warning that the body's mechanisms for dealing with heat are becoming overwhelmed.

Heat stroke

Heatstroke, on the other hand, is a more severe and life-threatening condition that occurs when the body's temperature regulation fails, leading to a rapid rise in body temperature, often above 104°F (40°C). Given the seriousness, it requires immediate medical attention.

Symptoms of Heatstroke and Heat Exhaustion

Heat exhaustion symptoms

  • Heavy sweating: Profuse sweating as the body attempts to cool itself.
  • Weakness or fatigue: Feeling unusually tired and weak.
  • Dizziness or fainting: Light-headedness or fainting due to decreased blood flow to the brain.
  • Nausea or vomiting: Feeling sick to the stomach or vomiting.
  • Muscle cramps: Painful cramps or spasms in muscles, typically in the legs or abdomen.
  • Cool, moist skin: Skin may feel cool and clammy despite the heat.
  • Weak, rapid pulse: Faster heart rate but weak in strength.
  • Headache: Generalised or specific pain in the head.

Heatstroke symptoms

  • Extremely high body temperature: Core body temperature above 104°F (40°C).
  • Altered mental state or behaviour: Confusion, agitation, slurred speech, irritability, delirium, or even seizures.
  • Nausea and vomiting: Intense feeling of Nausea and vomiting.
  • Flushed, hot, and dry Skin: Skin may be red, hot, and dry to the touch (sweating may be present if heatstroke is exertional).
  • Rapid, shallow breathing: Quick, shallow breaths.
  • Racing heart rate: Rapid and strong pulse.
  • Headache: Severe headache that doesn't go away.
  • Seizures: Involuntary convulsions.
  • Loss of Consciousness: Fainting or unconsciousness.

Recognizing these symptoms and understanding the differences between heat exhaustion and heatstroke can make a significant difference in responding appropriately and preventing serious health consequences.

Read more- Understanding Heatwaves: Their Effects on the Body and Who is at Risk

Risk Factors for Heatstroke and Heat Exhaustion

Certain factors can increase the likelihood of developing heat-related illnesses like heatstroke and heat exhaustion. Understanding these risk factors can help in preventing these conditions and ensuring timely intervention.

Heat exhaustion risk factors

  • High temperatures and humidity: Prolonged exposure to hot and humid weather increases the risk.
  • Physical activity: Engaging in strenuous activities, especially in the heat, can lead to heat exhaustion.
  • Dehydration: Inadequate fluid intake makes it difficult for the body to regulate temperature.
  • Age: The very young and the elderly are more susceptible due to their bodies' less efficient temperature regulation mechanisms.
  • Clothing: Wearing heavy, tight, or non-breathable clothing can hinder the body’s ability to cool down.
  • Medications: Certain medications, such as diuretics, antihistamines, and beta-blockers, can affect the body's heat regulation.
  • Health conditions: Chronic illnesses like heart disease, lung disease, and obesity can increase susceptibility.
  • Sudden temperature changes: Rapid changes from cooler to hotter environments can put stress on the body’s ability to adapt.
  • Alcohol consumption: Alcohol can lead to dehydration and impair the body's ability to regulate temperature.

Heatstroke risk factors

  • Prolonged exposure to extreme heat: Extended time spent in high temperatures, especially with high humidity, can overwhelm the body's cooling mechanisms.
  • Strenuous activity in heat: Vigorous physical activity in hot weather can lead to rapid body temperature increases.
  • Age: Infants, children under 4, and adults over 65 are at higher risk due to their bodies’ less efficient heat regulation.
  • Chronic illnesses: Conditions such as cardiovascular disease, respiratory disease, diabetes, and obesity increase the risk.
  • Medications: Certain drugs can interfere with the body's ability to stay hydrated and respond to heat, including diuretics, antihistamines, stimulants, and psychiatric medications.
  • Previous heat-related illness: Having had heat exhaustion or heat stroke before can increase susceptibility.
  • Lack of acclimatisation: Individuals not accustomed to high temperatures, such as tourists or new residents in hot climates, are more vulnerable.
  • Poor hydration: Inadequate intake of fluids can lead to dehydration, reducing the body’s ability to sweat and cool down.
  • Environmental factors: Living in urban areas with less green space and more concrete (which retains heat) can increase the risk.
  • Alcohol and drug use: Excessive alcohol consumption and use of certain drugs can impair the body’s heat regulation mechanisms.

By being aware of these risk factors, individuals can take preventative measures to reduce their likelihood of developing heat exhaustion or heatstroke, especially during periods of extreme heat.

How are Heat Exhaustion and Heat Stroke Diagnosed?

Heat exhaustion

Clinical evaluation

  • Medical history: The healthcare provider will take a detailed medical history, including recent activities, exposure to high temperatures, fluid intake, and symptoms.
  • Physical examination: The provider will assess vital signs (temperature, heart rate, blood pressure), look for signs of dehydration (dry mucous membranes, reduced skin turgor), and check for other symptoms like heavy sweating, muscle cramps, and weakness.

Diagnostic tests

  • Blood Tests: These may be done to check for electrolyte imbalances, dehydration, and kidney function.
  • Urine Tests: Urine analysis can help assess hydration status and kidney function.


Clinical evaluation

  • Medical history: Similar to heat exhaustion, the provider will review recent activities, exposure to heat, and symptom history. More emphasis is placed on changes in mental status or behaviour.
  • Physical examination: Vital signs are crucial, particularly body temperature (often above 104°F or 40°C). The provider will also check for neurological symptoms like confusion, seizures, and unconsciousness.

Diagnostic tests

  • Core body temperature measurement: This is often done with a rectal thermometer to get an accurate reading.
  • Blood tests: These are more extensive than for heat exhaustion. Tests will check for electrolyte imbalances, liver and kidney function, muscle damage (creatine kinase levels), and coagulation issues.
  • Urine tests: Urine analysis helps evaluate hydration status and can detect muscle breakdown (myoglobin).
  • Imaging tests: In severe cases, imaging like a CT scan may be done to assess for brain damage or other internal complications.

By using these diagnostic methods, healthcare providers can accurately differentiate between heat exhaustion and heatstroke and determine the appropriate treatment to ensure the best outcomes for the patient.

Read more- Understanding Heatstroke: Causes, Symptoms, and Treatment

What to do: Heat Exhaustion and Heatstroke

Knowing how to respond to heat exhaustion and heatstroke can help prevent the conditions from worsening and save lives. Here are the steps to take for each condition:

Heat exhaustion

Immediate actions

  • Move to a cooler place: Get the person out of the heat and into a cool or shaded area, preferably an air-conditioned environment.
  • Rest: Have the person lie down and rest.
  • Hydrate: Encourage drinking cool water or sports drinks to replenish lost fluids and electrolytes. Avoid alcohol or caffeinated beverages.
  • Cool the body: Use cool, wet clothes, or take a cool bath or shower. Apply cold packs to the armpits, neck, and groyne areas.
  • Loosen clothing: Remove tight or unnecessary clothing to help the body cool down.

Monitor symptoms

If symptoms improve within 30 minutes, continue to rest and hydrate. However, if symptoms do not improve or worsen, seek medical attention immediately as it may progress to heatstroke.


Immediate actions

  • Call emergency services: Heatstroke is a medical emergency. Dial emergency services immediately.
  • Move to a cooler place: Get the person out of the heat and into a cool or shaded area.
  • Rapid cooling: Use any available method to cool the person:
    • Immerse in cool water (bath, tub, or lake).
    • Apply ice packs to the armpits, neck, groyne, and back.
    • Use a cool shower, garden hose, or sponge with cold water.
  • Loosen clothing: Remove excess clothing to facilitate cooling.


If the person is conscious and able to drink, provide cool water or sports drinks. However, if the person is unconscious, do not attempt to give any fluids.

Monitor symptoms

Keep a close eye on the person's condition, checking for changes in consciousness and breathing. If the person loses consciousness and shows no signs of breathing, start CPR if trained to do so, or contact emergency services immediately.

Understanding and acting promptly on these steps can prevent the escalation of heat-related illnesses and ensure the well-being of individuals affected by extreme heat.

Preventing Heatstroke and Heat Exhaustion

Preventing heat-related illnesses involves taking proactive measures to avoid excessive heat exposure and ensuring the body can effectively regulate its temperature. Here are some key strategies:

Stay hydrated

  • Drink plenty of fluids: Consume water regularly, especially in hot weather or when exercising. Avoid alcohol and caffeinated beverages, which can contribute to dehydration.
  • Electrolyte replacement: Use sports drinks to replenish electrolytes lost through sweat during prolonged physical activity.

Dress appropriately

  • Wear lightweight, loose-fitting clothing: Choose clothes that allow your body to breathe and help sweat evaporate.
  • Go for light-coloured clothing: Light colours reflect, rather than absorb, the heat.

Limit sun exposure

  • Stay indoors during peak heat: Avoid outdoor activities during the hottest parts of the day, typically between 10 a.m. and 4 p.m.
  • Seek shade: When outside, stay in shaded areas as much as possible.
  • Use sunscreen: Apply sunscreen to protect your skin from sunburn, which can hinder your body’s ability to cool itself.

Plan physical activities wisely

  • Schedule workouts and outdoor activities: Perform strenuous activities during cooler parts of the day, such as early morning or late evening.
  • Take frequent breaks: Rest in a cool place to prevent overheating.

Acclimate to the Heat

  • Gradually Increase Exposure: Allow your body to adapt to high temperatures by gradually increasing the time spent in the heat over several days.
  • Conditioning: If you are new to a hot climate, give yourself time to adjust before engaging in strenuous activities.

Use cooling techniques

  • Use fans and air conditioning: Keep indoor spaces cool using fans, air conditioning, or evaporative coolers.
  • Take cool showers or baths: Use water to help lower your body temperature.

Recognize warning signs

  • Know the symptoms: Be aware of the symptoms of heat exhaustion and heatstroke, such as heavy sweating, dizziness, nausea, rapid pulse, confusion, and high body temperature.
  • Act quickly: If you or someone else shows signs of heat-related illness, take immediate action to cool down and seek medical attention if necessary.

Be cautious with medications

  • Check medication side effects: Some medications can affect the body’s ability to regulate temperature. Consult with your healthcare provider about any potential risks.

By taking these preventative measures, you can significantly reduce the risk of heat exhaustion and heatstroke, ensuring you stay safe and healthy during periods of extreme heat.

When to see a Healthcare Provider?

For heat exhaustion, see a healthcare provider if symptoms like heavy sweating, weakness, dizziness, nausea, or headache persist or worsen after 30 minutes of cooling down and rehydration. If severe symptoms develop, such as confusion, vomiting, or fainting, or if the person has pre-existing conditions like heart disease or diabetes, seek medical advice promptly. 

For heatstroke, seek emergency medical attention immediately if the person has a body temperature of 104°F (40°C) or higher, shows an altered mental state, experiences severe symptoms like rapid, shallow breathing or a racing heart rate, or stops sweating. Immediate action is crucial for severe cases to ensure prompt and effective treatment.

Final words

Recognizing and promptly addressing heat-related illnesses can save lives and prevent serious complications. If you or someone you know experiences symptoms of heat exhaustion or heatstroke, don't hesitate to seek professional medical help. Max Hospitals is equipped with specialised care and expert medical staff to provide the necessary treatment for heat-related conditions. Consulting a specialist at Max Hospitals ensures you receive comprehensive care tailored to your needs, helping you recover safely and swiftly. Stay vigilant, stay hydrated, and prioritise your health by trusting the experts at Max Hospitals for all your medical concerns.