Heat Stroke

Overview

Heat stroke is a severe and life-threatening condition where your body overheats, often to a temperature of 40°C (104°F) or higher. It happens when the body's heat-control system fails, and it can damage the brain, heart, kidneys, and muscles without quick treatment.

True heat stroke is less common than milder heat-related illnesses like heat exhaustion, but it becomes more frequent during heatwaves and in very hot climates.

Anyone can get heat stroke, but it is most risky for older adults, very young children, people with chronic health conditions, and those who work or exercise outdoors in hot weather.

Symptoms

Common symptoms

• Very high body temperature (often above 40°C or 104°F)
• Hot, dry skin that may be flushed but not sweating (sweating may stop)
• Confusion, agitation, slurred speech, or even loss of consciousness
• Severe headache
• Nausea and vomiting
• Rapid, shallow breathing
• Fast heart rate

Symptoms in children

• Fever and hot skin that may be dry or moist
• Irritability or drowsiness
• Refusing to drink
• Rapid breathing or panting
• Seizures (fits) in severe cases

Symptoms in older adults

• High temperature but may not feel hot to the touch
• Confusion or unusual behavior
• Weakness and dizziness, falling
• Dry or slightly moist skin
• Rapid heartbeat and breathing

Causes

Main causes

• Spending too long in very high temperatures, especially with high humidity
• Strenuous physical work or exercise in hot weather
• Not drinking enough fluids to replace water lost through sweat
• Wearing heavy clothing that prevents sweat evaporation

Risk factors

• Age: very young or older adults are more vulnerable
• Certain medications that affect the body's ability to stay cool or sweat
• Chronic illnesses like heart disease, diabetes, or obesity
• Drinking alcohol or using drugs that dehydrate the body
• Previous heat-related illness makes you more likely to have it again

When to see a doctor

See a doctor urgently if:

• If you or someone else shows any signs of heat stroke, even mild confusion or hot dry skin, seek immediate medical help – this is an emergency.

Book a routine appointment if:

• After recovering from a heat-related illness, a follow-up with your doctor is wise to ensure no lasting damage, especially if you have existing health conditions.

Diagnosis

Doctors usually diagnose heat stroke by checking your symptoms, taking your temperature (often with a rectal thermometer for the most accurate reading in an emergency), and examining your nervous system function.

Tests that may be done

• Measuring core body temperature
• Blood tests to check for electrolyte imbalances and organ function
• Urine tests to see how your kidneys are working
• Sometimes imaging tests of the brain (CT scan) if there is confusion or unconsciousness

What to expect at your appointment

If you are taken to hospital with suspected heat stroke, the medical team will act quickly to cool you down while running tests. This can feel overwhelming, but it is the best way to protect your health.

Treatment

Heat stroke needs immediate, aggressive cooling. While waiting for emergency help, move the person to a cool place and start cooling them quickly. In the hospital, doctors continue cooling and support the body's organs.

Self-care at home

• Move the person to a cooler spot, like shade or air-conditioning.
• Remove excess clothing.
• Apply cool, wet cloths or ice packs to the neck, armpits, and groin.
• Fan the person while spraying with cool water if possible.
• If they are conscious and can swallow, give small sips of cool water. Do not force fluids if confused.

Medical treatments

Hospital treatment may include cold intravenous (IV) fluids to lower temperature and improve hydration, cooling blankets or immersion in cool water, and careful monitoring of the heart, kidneys, and brain. Doctors will treat any complications as they arise. They do not typically use standard fever-reducing medicines because they do not work for heat stroke.

Living with this condition

After recovering from heat stroke, you may feel tired or weak for a while. It is important to take it easy, stay in a cool environment, and drink plenty of fluids. Avoid hot environments for at least a week.

Lifestyle tips

• Plan outdoor activities for cooler times of the day.
• Wear lightweight, loose-fitting, light-coloured clothing.
• Take frequent breaks in the shade or air conditioning.
• Monitor the colour of your urine – pale yellow means you're well-hydrated.

Diet and exercise

Eat light meals, like fruits and vegetables, that contain water. When exercising, drink before you feel thirsty and take rest breaks. Avoid alcohol and heavy, high-protein foods that can increase body heat.

Mental health and emotional wellbeing

A frightening experience like heat stroke can leave you feeling anxious or worried. It's normal to have some fear about being in the heat again. Talking about your feelings with a friend or a mental health professional can help. Seek support if you feel persistently low or anxious.

Prevention

Yes, heat stroke can almost always be prevented by taking simple precautions in hot weather.

Complications

If left untreated

• Damage to the brain, causing lasting confusion or memory problems
• Kidney failure
• Liver damage
• Muscle tissue breakdown (rhabdomyolysis), which can harm the kidneys
• Lung problems or breathing difficulties
• Death

Long-term outlook

With fast and effective cooling, most people recover fully from heat stroke. However, some may experience lingering sensitivity to heat or need time to regain strength. Quick action – cooling the person right away and getting emergency help – makes the biggest difference.

Find support

International organisations

• World Health Organization (WHO) – Heat and health ↗

Local organisations

• NHS – Heat exhaustion and heatstroke ↗ · United Kingdom

Helplines

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