Heat Exhaustion or Heatstroke? Warning Signs, First Aid, and When to Call 112
Hot weather can affect the body much faster than many people realise. What begins as thirst, sweating or tiredness can progress to confusion, collapse or a life-threatening medical emergency.
Two of the most important heat-related conditions are heat exhaustion and heatstroke. Although they may begin with similar symptoms, they are not the same. Heat exhaustion requires immediate cooling and hydration, while heatstroke requires emergency medical treatment.
Knowing the difference could save a life.
Emergency warning: If someone becomes confused, has a seizure, loses consciousness or appears severely unwell after heat exposure, call 112 immediately.
What Is Heat Exhaustion?
Heat exhaustion happens when the body loses too much water and salt, usually through heavy sweating. It may develop after spending a long time in hot weather, exercising in the heat or working in a hot environment.
Common warning signs include:
- Heavy sweating
- Intense thirst
- Headache
- Dizziness or light-headedness
- Weakness or unusual tiredness
- Nausea or vomiting
- Muscle cramps
- Pale, cool or clammy skin
- Fast heartbeat or breathing
- Reduced urine output
The person is generally still awake and able to communicate, although they may feel weak, irritable or faint. Heat exhaustion can quickly progress to heatstroke if the person is not cooled and rehydrated.
What Should You Do for Heat Exhaustion?
Act immediately:
- Move the person into a cool, shaded or air-conditioned place.
- Help them lie down and rest.
- Remove unnecessary outer clothing and loosen tight clothing.
- Cool their skin with cool water, wet towels or a fan.
- Place wrapped cold packs around the neck or under the armpits.
- Give cool water or an oral rehydration drink if the person is fully awake and able to swallow safely.
- Stay with them and continue monitoring their condition.
Do not place ice or frozen cold packs directly against the skin because this may damage the skin. Wrap them in a cloth first.
The person should begin to feel better after cooling and resting. Seek urgent medical advice if they are not clearly improving within about 30 minutes, if their symptoms worsen, or if you are uncertain about their condition.
What Is Heatstroke?
Heatstroke occurs when the body can no longer control its temperature effectively. The body becomes dangerously overheated, and vital organs—including the brain, heart and kidneys—may be damaged.
Heatstroke is a medical emergency and can be fatal without rapid treatment.
Warning signs may include:
- Confusion or unusual behaviour
- Difficulty speaking or slurred speech
- Poor coordination or inability to walk normally
- Collapse or loss of consciousness
- Seizures
- Very hot skin
- A very high body temperature
- Fast breathing
- A rapid heartbeat
- Severe headache
- Nausea or vomiting
A person with heatstroke may have hot, dry skin, but this is not always the case. Some people—particularly those who develop heatstroke during exercise or physical work—may continue sweating. Therefore, do not wait for sweating to stop before taking action.
The most important danger sign is a change in mental state, such as confusion, disorientation, unusual behaviour, seizure or unconsciousness.
What Should You Do for Suspected Heatstroke?
Call 112 immediately.
While waiting for the emergency service:
- Move the person into shade or a cooler place.
- Remove unnecessary outer clothing.
- Cool the person rapidly with cool water, wet towels or continuous spraying.
- Fan the wet skin to increase cooling.
- Apply wrapped cold packs around the neck, under the armpits and around the groin.
- Stay with the person and monitor their breathing.
- Place an unconscious but breathing person in the recovery position.
- Begin CPR if the person is not breathing normally and you know how to perform it.
Do not give food, water or other drinks to someone who is confused, having a seizure, unconscious or unable to swallow safely. They could choke.
Do not delay calling emergency services while trying to measure the person’s temperature. If their behaviour or consciousness has changed after heat exposure, treat the situation as an emergency.
Heat Exhaustion vs. Heatstroke: The Main Difference
With heat exhaustion, the person is usually awake, sweating and able to communicate, although they may be very weak, thirsty, dizzy or nauseated.
With heatstroke, the person’s brain function becomes affected. Confusion, strange behaviour, difficulty speaking, seizures or loss of consciousness are major emergency signs.
A simple way to remember the difference is:
Weak, sweaty and dizzy: begin cooling immediately.
Confused, collapsing or unconscious: call 112 immediately.
When you are uncertain, it is safer to seek urgent medical help.
Who Is Most at Risk?
Anyone can develop a heat-related illness, but certain people require additional protection:
- Babies and young children
- Older adults
- People living with heart, kidney, respiratory or metabolic conditions
- People with diabetes
- People taking medicines that affect hydration, sweating or temperature regulation
- Outdoor workers
- Athletes and people exercising in hot weather
- People who are not accustomed to hot conditions
- People living alone or without access to a cool environment
Some medicines can increase vulnerability to heat or dehydration. Do not stop prescribed medication by yourself. Speak with your doctor or pharmacist about how to manage your medication safely during very hot weather.
How to Reduce Your Risk During Hot Weather
You can lower your risk by taking a few practical precautions:
- Drink fluids regularly rather than waiting until you feel extremely thirsty.
- Avoid excessive alcohol during hot weather.
- Limit strenuous activity during the hottest part of the day.
- Wear light, loose-fitting clothing.
- Rest regularly in shade or a cool indoor space.
- Use cool showers, wet towels or fans to help lower body temperature.
- Check on older relatives, neighbours and people living alone.
- Never leave a child, older person or animal inside a parked vehicle.
- Pay attention to headache, dizziness, nausea, weakness and unusual tiredness.
The World Health Organization recommends seeking shade, taking cooling breaks and watching carefully for symptoms such as dizziness, nausea or confusion during periods of extreme heat.
Final Message
Heat exhaustion is a serious warning that the body is struggling with heat. Heatstroke means the body’s temperature-control system is failing and emergency treatment is required.
Do not dismiss unusual weakness, dizziness, confusion or collapse as “just the heat.” Begin cooling immediately, stay with the affected person and call 112 whenever heatstroke is suspected.
Recognising the warning signs early—and acting without delay—could save a life.
Medical Disclaimer
This article provides general health education and is not a substitute for medical diagnosis, emergency treatment or personalised medical advice. In a medical emergency, call 112 or your local emergency service immediately.
For non-emergency support with hydration, healthy routines, chronic-condition management and practical lifestyle changes, visit WellNest Central to learn about our holistic health consultations.