Heat Stroke: Symptoms, Risks, Prevention, First Aid & Treatment

Medically Reviewed by Dr. Sony Sherpa, (MBBS) – June 26, 2025

Introduction

What is heat stroke?

A severe form of heat-related illness, heat stroke occurs when the body’s core temperature rises to dangerous levels, overwhelming its natural cooling mechanisms. When the body’s core temperature reaches 104°F (40°C) or higher, it leads to serious symptoms such as a headache, altered mental state, rapid breathing, and a racing heart rate.

During the hot summer months, our bodies are more susceptible to heat-related illnesses, with heat stroke being one of the most severe conditions that can lead to unconsciousness and death without timely intervention. According to a study published in The Lancet, it is a leading cause of weather-related mortality worldwide, with an estimated 56,000 heat stroke deaths per year.

Heat exhaustion (early-stage overheating) can be treated with rest and hydration, while severe cases require emergency medical attention. Severe heat stroke can negatively impact many areas of the body and cause multiple organ dysfunction, leading to potentially fatal consequences if not promptly addressed.

As global temperatures continue to rise, it is essential to understand the signs, symptoms, and preventive measures to avoid potentially life-threatening consequences.

What are the types of heat stroke?

Heat stroke is often classified into two types:

Exertional heat stroke

Caused by prolonged intense physical activity in a hot environment, it usually affects younger, healthy individuals who overexert themselves, such as athletes and soldiers.

Non-exertional heat stroke (classic heat stroke)

This type is caused by prolonged exposure to hot and humid weather. It commonly affects the elderly and those with chronic illnesses who battle to regulate their temperature when overheated.

Symptoms, Causes, Risk Factors

What are the symptoms associated with heat stroke?

Recognizing the early signs of heat stroke is crucial to quickly prevent further complications and possible mortality.

Common symptoms of heat stroke include:

• Body temperature of 104°F (40°C) or higher
• Hot, dry, and flushed skin in the absence of sweating (classic heat stroke) or heavy sweating (due to exertion)
• Swollen and dry tongue
• An unusually rapid heart rate and breathing (tachycardia and hyperventilation)
• Nausea and vomiting
• Throbbing headache
• Muscle cramps and weakness
• Lack of physical coordination
• Signs of an altered mental state, such as irritability, confusion, and agitation
• Neurologic symptoms (in severe cases), such as slurred speech, seizures, and loss of consciousness.

Symptoms of heat exhaustion are often less intense and can include a headache, dizziness, nausea, and muscle cramps.

Heat stroke symptoms in kids are similar to the signs of heat stroke in adults. Children are more vulnerable to heat stroke since, unlike adults, they are less able to regulate their temperature. Their smaller bodies and reduced ability to sweat may contribute to a quicker heat stroke onset in children.

How does a heat stroke typically feel?

In the early stages, heat stroke may feel like dizziness, disorientation, fatigue, muscle cramps, and nausea. As the condition progresses, symptoms intensify and may involve a pounding headache, lack of sweating, and altered mental status, such as confusion or fainting.

What are the causes of heat stroke?

The extreme overheating that leads to heat stroke can be caused by any factors that detract from the body’s ability to cool itself down.

Body Cooling Mechanisms

The main cooling mechanisms affected by heat stroke include:

Blood circulation and evaporation: Core body temperature is regulated by the transfer of heat from the inner compartments to the skin. Heated blood from the core body tissues moves through specialized blood vessels in the extremities (palms, feet, neck, and head) and reaches the skin, where heat is lost due to radiation (via vasodilation) and evaporation (via sweating). For this to work properly, the skin’s temperature needs to be kept cooler than the core body temperature.

Neuroregulation: Vasodilation, blood circulation, heat loss through the skin, and sweating rely on neurological feedback between the hypothalamus in the brain and the body at large. When exposed to high temperatures, the brain signals an elevated heart rate to promote skin cooling and a reduced metabolic rate to lower core heat production. This is why we can feel fatigued in the heat.

How body cooling is overwhelmed due to heat stroke

During a classic heat stroke, the environmental temperature is high enough to overwhelm the skin, preventing it from radiating heat. During exertional heat stroke, the core body temperature rises due to physical activity, exceeding the body’s cooling abilities. If the humidity is high enough (over 75%), it can further detract from heat loss by stifling evaporation through sweating.

In this respect, the early symptoms of heat stroke are signs of failed body cooling, such as dry skin, an increased heart rate, and intense, throbbing headaches due to the extreme dilation of blood vessels. Heat starts to denature internal proteins and leads to excessive inflammation that can further deregulate bodily cooling mechanisms and give way to muscle cramps, weakness, and multiple organ damage and failure. Patients may be unable to regulate their temperature for several weeks to months after suffering a heat stroke.

Who is most at risk of developing heat stroke?

Individuals with compromised body cooling mechanisms are more likely to acquire a heat stroke. These include:

• The elderly
• Children
• Patients with chronic inflammatory diseases or neurologic disorders

A higher proportion of those with hypertension or heart disease are known to suffer from the long-term effects of heat stroke and are at a higher risk of mortality.

Other factors that place a person at risk for heat stroke include:

• Chronic health conditions such as diabetes, active infections, and obesity
• Various medications (see next section)

Medications and substances that make you more susceptible to heat stroke

• Diuretics
• Heart medications
• Antihistamines

Diagnosis

How do doctors diagnose heat stroke?

Heat stroke is primarily diagnosed based on clinical signs and a person’s recent exposure to high temperatures or vigorous physical activity in a hot environment. A healthcare provider will assess symptoms such as an elevated core body temperature (above 104°F or 40°C), altered mental state, lack of sweating, and other heat-related indicators. Medical history, including the timing and nature of heat exposure, plays a crucial role in identifying the condition. A physical examination will focus on neurological status, skin condition, and vital signs to evaluate the severity of the heat-related illness.

Role of Testing

To confirm the diagnosis and assess organ function, several tests may be performed:

• Core body temperature is typically measured using a rectal thermometer, as it provides the most accurate internal temperature.
• Blood tests help evaluate electrolytes, kidney function, and potential muscle damage by checking creatine kinase levels.
• Urinalysis may indicate dehydration or muscle breakdown.
• Imaging tests (e.g., chest X-rays or CT scans) are used in some cases to rule out other causes of symptoms or to detect complications like swelling or internal damage.
• Electrocardiogram (ECG) may be used to monitor heart function, especially in severe cases or for those with underlying cardiovascular conditions.

These evaluations guide immediate treatment and help prevent complications by monitoring the effects of heat stroke on multiple body systems.

First Aid and Treatment

What is involved in the treatment of heat stroke?

If you or someone you know displays heat stroke signs or symptoms, it is essential to act immediately. Knowing what to do can help to minimize potential damage before admitting the person to a hospital.

The chances of recovery can be increased by taking the following steps:

Heat stroke first aid

Call for Emergency Help

If you suspect someone has a heat stroke, call emergency services right away. Basic heat stroke treatment at home – as explained below – can be vital while waiting for help.

Move to a Cooler Area

First aid for heat stroke entails cooling the person down and ensuring they can breathe. Get the person out of the heat and into an air-conditioned or shaded environment.

Cool the Body

Use cool water, ice packs, wet cloths, or fans to lower the person’s body temperature. Focus on the neck, palms, feet, armpits, and groin. If the patient is not suffering from heart disease or hypertension, it can be a good idea to immerse them in a cold water bath until an ambulance arrives. This is highly effective at quickly lowering core body temperature and can avoid potential mortality. It is important to monitor their temperature, avoid overcooling, and make sure they can still breathe.

Hydration

Heat stroke can cause severe dehydration. If the person is conscious and able to swallow, you can try to provide cool water or water enriched with electrolytes. It is very likely that they will need to be hospitalized until they are rehydrated and stable.

How is heat stroke treated at the hospital?

Even if the person’s condition improves, do not cancel emergency help or delay taking them to a hospital for further evaluation. They may still require medical attention to prevent later complications. Hospital treatments may include:

• Intravenous infusion of cooled fluids
• Seizure preventive medications
• Oxygen supplementation therapy
• Cold-water lavage

It is important to seek medical attention immediately if you suspect that you or someone else is experiencing symptoms of a heat stroke. This includes mild heat stroke as well, as the person may still suffer from complications or long-term effects of heat stroke.

Recovery and Outlook

What is the prognosis following a heat stroke episode?

Recovery and prognosis depend on:

• The cause of the heat stroke
• How quickly it was addressed
• The person’s age and overall health

Mortality Rates:

• Classic heat stroke: 10–65%
• Exertional heat stroke: 3–5% (often preventable with proper cooling)

How long is the recovery period following heat stroke?

In non-fatal cases, full recovery is usual. How long a heat stroke lasts depends on the severity of the case.

• Mild cases: Recovery within a few days to a week.
• Severe cases: Recovery may take up to 7 weeks or more.
• Delayed mortality: Can occur up to 2 years post-recovery.
• Medication requirements: Some may need long-term use of heart medications or anticoagulants to manage complications.

What are the possible complications and long-term effects of heat stroke?

Heat strokes can cause long-term damage to the body, including injury to the:

• Brain
• Heart
• Liver
• Kidneys (especially vulnerable)

Other possible heat stroke complications include:

The long-term effects of heatstroke can be severe and can affect a person’s health for the rest of their life by reducing their tolerance to environmental stressors and increasing their risk for acquiring lifestyle diseases, such as Atherosclerosis.

Preventive Measures

How to prevent heat stroke

Prevention combines awareness and practical steps to stay cool and hydrated:

• Stay Hydrated:
  
  Even if you do not feel thirsty, make sure to consume lots of fluids, particularly water, and drinks high in electrolytes. Older individuals and those who do not ordinarily drink adequate water need to pay special attention to how much they drink per day.
• Dress Appropriately:
  
  Dress comfortably, wearing lightweight and loose-fitting clothes that allow your skin to breathe. It is also a good idea to wear lighter-colored clothing, as it reflects more light and heat, keeping you cool throughout the day. Furthermore, it is advisable to apply sunscreen to exposed skin.
• Limit Outdoor Activities:
  
  Avoid engaging in vigorous outdoor activities when it’s hot outside. If you must be outside, take frequent breaks in the shade or indoors. Always carry water and keep hydrating yourself.
• Avoid Overly Hot Environments:
  
  There are many scenarios that can cause heat stroke, most of which depend upon an individual’s heat tolerance and hydration status. Saunas, hot springs, heated pools, baths, and showers are all heated environments that can promote heat stroke in individuals who are at risk. It is advisable not to leave pets and children in a parked car on a hot day, as temperatures inside a vehicle can become dangerously high.

Related Conditions

Heat Stroke vs. Heat Exhaustion

To compare and contrast heat exhaustion and heat stroke, both heat-related conditions, it is essential to understand their distinct differences in terms of symptom presentation and severity.

Heat Exhaustion is milder than heat stroke and usually occurs preemptively. It is characterized by excessive sweating, pale and damp skin, weakness, dizziness, nausea, anxiety, and restlessness. Sometimes, one may get a heat rash or experience swelling of the ankles (edema). While it is a serious condition, it is not as extreme as heat stroke and does not usually involve the same altered mental state. Heat exhaustion can often be managed by moving to a cooler place, rehydrating, and resting.

Heat Stroke is a medical emergency that requires treatment right away. By comparison to heat exhaustion, those with heat stroke do not sweat or have moist skin, suffer from an altered mental state, and experience more extreme symptoms where they overlap. Heat stroke demands swift cooling measures and medical intervention to prevent organ damage, long-term complications, and potential fatality.

Is sunstroke the same as heat stroke?

Sunstroke can be viewed as a specific type of heat stroke that occurs when the body is exposed to direct sunlight. Heat stroke, in general, can occur with or without sunlight. The symptoms of sunstroke are the same as those of heat stroke and may include extreme sunburn as well.

Conclusion

Heat stroke is a serious medical emergency that requires swift action to prevent severe complications that can lead to fatality. Preventive measures against heat and awareness of the warning signs and symptoms are crucial to staying safe in hot weather. By following these guidelines, you can enjoy the summer months while keeping heat-related illnesses at bay.

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About the Mya Care Editorial Team:

About the Reviewer:

Dr. Sony Sherpa completed her MBBS at Guangzhou Medical University, China. She is a resident doctor, researcher, and medical writer who believes in the importance of accessible, quality healthcare for everyone. Her work in the healthcare field is focused on improving the well-being of individuals and communities, ensuring they receive the necessary care and support for a healthy and fulfilling life.

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