Heat Stroke vs Hypothermia — Recognition & Response

Both heat stroke and hypothermia are life-threatening emergencies that can develop quickly and look like less serious conditions early on. Correct identification is essential — the treatments are opposite.

⚠️ Treating heat stroke with warmth, or hypothermia with cold water, will kill. Identify which condition is present before acting.

At a Glance — The Key Differences

Feature	Heat Exhaustion	Heat Stroke	Mild Hypothermia	Severe Hypothermia
Core temperature	Elevated	>40°C / 104°F	32–35°C / 90–95°F	<32°C / 90°F
Skin	Pale, cool, clammy	Hot, red, dry or damp	Pale, cold	Pale, cold, may be mottled
Sweating	Heavy sweating	Often absent (dry heat stroke)	Shivering present	Shivering stops
Consciousness	Alert but weak	Confused, combative, may be unconscious	Alert but confused	Unconscious or semi-conscious
Breathing	Normal to rapid	Rapid, shallow	Slow	Very slow, weak
Emergency level	Urgent	Life-threatening — call 999/911	Urgent	Life-threatening — call 999/911

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Heat Exhaustion — Recognition & Response

Not yet life-threatening, but can progress to heat stroke rapidly.

Signs

• Heavy sweating
• Cool, pale, clammy skin
• Fast, weak pulse
• Nausea or vomiting
• Muscle cramps
• Tiredness and weakness
• Dizziness
• Headache
• Fainting

Response

1. Move the person to a cool place (shade, air conditioning)
2. Lay them down and elevate the legs slightly
3. Remove excess clothing
4. Cool them — cold wet cloths on neck, armpits, and groin; fan them
5. Give cool water to sip if conscious and able to swallow
6. Monitor closely — if symptoms worsen or do not improve within 30 minutes, call emergency services

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Heat Stroke — Recognition & Response

Life-threatening. Core temperature >40°C. Call 999/911 immediately.

Signs

• Body temperature above 40°C (104°F)
• Hot skin — often red; may be dry (classic heat stroke) or damp (exertional heat stroke)
• Confusion, disorientation, slurred speech
• Loss of consciousness
• Rapid strong pulse
• Absence of sweating (in classic heat stroke)
• Seizures

Response

Step	Action
1. Call 999/911 immediately	This is a medical emergency
2. Move to cool environment	Indoors with air conditioning; shade if indoors not available
3. Cool aggressively and immediately	Ice packs to neck, armpits, groin; immerse in cold water if available; wet sheets and fan
4. Do not give fluids	An unconscious or confused person may aspirate
5. If unconscious and breathing	Recovery position; monitor airway
6. If not breathing	Begin CPR

Do not: Give paracetamol or aspirin — they do not work for heat stroke and may worsen it.

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Mild Hypothermia — Recognition & Response

Core temperature 32–35°C. Person is conscious and shivering.

Signs

• Shivering (body's attempt to generate heat)
• Cold, pale skin
• Slurred speech
• Lack of coordination, stumbling
• Confusion, poor judgement

Response

1. Move to a warm, dry shelter
2. Remove wet clothing
3. Cover with blankets — include the head
4. Give warm (not hot) sweet drinks if conscious and able to swallow
5. Apply chemical heat packs to neck, armpits, and groin — not direct to skin
6. Keep them awake and moving if possible
7. Monitor for deterioration

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Severe Hypothermia — Recognition & Response

Core temperature <32°C. Person may be unconscious. Call 999/911 immediately.

Signs

• Shivering has stopped (a dangerous sign)
• Severe confusion or unconsciousness
• Stiff muscles
• Very slow, weak breathing
• Faint or absent pulse
• Skin may appear blue or mottled

Response

Step	Action
1. Call 999/911 immediately	Hospital rewarming is required
2. Handle very gently	Cold heart muscle is prone to fatal arrhythmia — rough handling can trigger cardiac arrest
3. Move to shelter	Carefully and slowly — minimise movement
4. Insulate	Wrap in blankets including the head; protect from ground cold
5. Do not rub limbs	Drives cold blood to core
6. Do not apply direct heat	Hot water bottles or heating pads can cause burns and worsen outcome
7. If no pulse or not breathing	Begin CPR — even very cold patients can survive with proper rewarming

"Not dead until warm and dead." — Continue CPR on a hypothermic patient until hospital rewarming confirms death.

Quick Reference

Condition	Key Sign	Immediate Action
Heat exhaustion	Heavy sweating, pale clammy skin, conscious	Cool environment; cool cloths; elevate legs; water to sip
Heat stroke	Hot red skin, confused or unconscious, temp >40°C	Call 999/911; aggressive cooling immediately
Mild hypothermia	Shivering, confused, temp 32–35°C	Warm shelter; dry clothes; blankets; warm drinks
Severe hypothermia	No shivering, unconscious, temp <32°C	Call 999/911; gentle handling; insulate; CPR if needed