--- title: "Heat exhaustion and heatstroke: Symptoms & Treatment" description: "How to recognise heat exhaustion and heatstroke, first aid, and when to call 999 in hot weather." url: https://healthanswers.co.uk/conditions/heat-exhaustion-and-heatstroke/ robots: noindex --- # Heat exhaustion and heatstroke: Symptoms & Treatment Health A–Z How to recognise heat exhaustion and heatstroke, first aid, and when to call 999 in hot weather. Written by HealthAnswers editorial team Medically reviewed by [HealthAnswers UK doctor review panel](https://healthanswers.co.uk/our-doctors/) Reviewed 3 July 2026 ## Quick answer What are heat exhaustion and heatstroke? Heat exhaustion happens when the body overheats — causing heavy sweating, dizziness, nausea and headache. Move to a cool place, drink fluids, and rest. Heatstroke is an emergency — the body stops cooling itself, skin may be hot and dry, and confusion or collapse can follow. Call 999 for heatstroke or if heat exhaustion does not improve within 30 minutes. ## Who is this page for? This page is for people in the UK who want a plain-English overview of Heat exhaustion and heatstroke, including when to seek help and what NHS care usually involves. It explains general information, not what is wrong with you personally. ## Who should skip this page? Skip this page if you need a diagnosis, a prescription, or emergency care. It cannot replace a GP, pharmacist, NHS 111 or 999. If you are in immediate danger, call 999; for urgent advice that is not life-threatening, call 111 in England, Scotland or Wales, or use your GP out-of-hours service in Northern Ireland. On this page 10 sections ## Key facts about heat exhaustion and heatstroke - Heat exhaustion is serious but usually reversible with cooling and fluids. - Heatstroke is life-threatening — call 999 immediately. - Elderly people, babies, and those with heart or lung conditions are most vulnerable. - Drink plenty of fluids in hot weather — do not wait until thirsty. - Never leave anyone in a parked car in warm weather. ## Hot weather can be dangerous In heatwaves and hot summer days, the body can struggle to cool itself — especially for vulnerable people. **Heat exhaustion** is overheating with symptoms that usually improve with cooling and fluids. **Heatstroke** is a life-threatening emergency where the body’s temperature regulation fails. Knowing the difference saves lives. ## Heat exhaustion — symptoms Heat exhaustion develops after prolonged exposure to heat, especially with dehydration or exertion: - headache - dizziness and confusion - nausea and vomiting - heavy sweating - pale, clammy skin - muscle cramps - fast breathing and pulse - intense thirst - weakness and fatigue - temperature above 38°C — usually below 40°C Heat exhaustion is serious but usually **reversible** with prompt cooling. ## What to do for heat exhaustion - Move to a cool place — shade, air-conditioned room, or cool bath - Lie down and raise feet slightly - Remove unnecessary clothing - Cool the skin — fan, cool wet sponges on neck and armpits, cool packs - Drink water or oral rehydration solution — sip slowly - Rest until symptoms improve — usually within 30 minutes If not improving within 30 minutes, or if vomiting prevents drinking → **call 999** (may be progressing to heatstroke). ## Heatstroke — a medical emergency Heatstroke occurs when core body temperature rises above **40°C** and the body’s cooling mechanisms fail. It can develop from untreated heat exhaustion or rapidly in extreme heat with exertion. **Call 999 immediately** if someone has: - hot skin — may be dry OR still sweating (exertional heatstroke in athletes may present with sweating) - confusion, agitation, or slurred speech - loss of consciousness or collapse - seizures - not responding normally - very high temperature - rapid heartbeat Heatstroke can cause organ damage and death without emergency treatment. ## First aid for heatstroke while waiting for ambulance - move to coolest available place - remove outer clothing - cool aggressively — ice packs in armpits and groin, cool wet sheets, fan while wetting skin - if conscious, offer sips of cool water - do not give aspirin or paracetamol — they do not help heat illness - place in recovery position if unconscious but breathing - start CPR if not breathing normally ## Who is most at risk - babies and young children — cannot regulate temperature well - older adults — especially over 75, living alone, or with limited mobility - chronic illness — heart, lung, kidney disease, diabetes - medications — diuretics, antihistamines, beta-blockers, antipsychotics (reduce sweating or thirst) - physical exertion in heat — athletes, outdoor workers - alcohol — increases dehydration and impairs judgement ## Preventing heat illness - drink regularly — water, diluted squash; avoid excess alcohol - stay indoors during peak heat (11am to 3pm) if vulnerable - wear light, loose clothing and a hat - use sunscreen — sunburn reduces sweating - never leave anyone in a parked car — temperatures rise fatally within minutes - check on elderly neighbours and relatives in heatwaves - keep bedrooms cool — close curtains, use fans ## Heat exhaustion in children Children overheat faster. Ensure regular drinks, shade, and lighter activity in peak heat. Seek help if a child is floppy, unusually drowsy, not drinking, or not improving after cooling. ## After a heat illness episode See a GP if you do not feel fully recovered within a few days. Repeat episodes suggest need for better prevention strategies — especially if on medicines that increase risk. ## Note on related link If you feel unwell from fluid loss without heat exposure, see guidance on gastroenteritis and oral rehydration. Heat illness specifically relates to environmental temperature overwhelming the body’s cooling capacity. ## ! When to see a GP about heat exhaustion and heatstroke Call **999 immediately** for heatstroke — hot dry skin, confusion, collapse, seizures, or loss of consciousness. For heat exhaustion, move to cool shade, remove excess clothing, cool with fans and wet sponges, and drink water or rehydration salts. If not improving within 30 minutes, or if vomiting prevents drinking, call 999. See a GP after a heat illness episode if you feel unwell for days afterward. ## Common questions about heat exhaustion and heatstroke What is the difference between heat exhaustion and heatstroke? Heat exhaustion — heavy sweating, pale clammy skin, dizziness, nausea, still sweating. Heatstroke — body temperature above 40°C, hot skin (may be dry or still sweating), confusion, collapse, seizures. Heatstroke is a medical emergency — call 999. What are the symptoms of heat exhaustion? Headache, dizziness, nausea, heavy sweating, pale clammy skin, cramps, fast pulse, intense thirst, and feeling weak or faint. Core temperature may be raised but usually below 40°C. How do you treat heat exhaustion? Move to a cool place, lie down with feet raised, remove unnecessary clothing, cool skin with fans and cool wet sponges on neck and armpits, drink water or oral rehydration solution slowly. Most people improve within 30 minutes. Who is most at risk in hot weather? Babies and young children, people over 75, those with heart, lung or kidney disease, diabetes, mobility problems, and people on medicines that reduce sweating (some antihistamines, antipsychotics, diuretics). Athletes and outdoor workers also at risk. How can I prevent heat illness? Drink regularly (not just when thirsty), avoid alcohol, stay in shade during peak heat (11am to 3pm), wear light clothing and hat, use sunscreen, and never leave people or pets in parked cars. ## Sources - [NHS — Heat exhaustion and heatstroke](https://www.nhs.uk/conditions/heat-exhaustion-heatstroke/)