On this page
Dr. Chrysoula I. Liakou MD, PhD
- Treated online: Partly. Heat exhaustion needs first aid on the spot; a doctor by video then checks recovery and your risk.
- Heat exhaustion: heavy sweating, pale clammy skin, dizziness, headache, nausea, cramps and strong thirst.
- First aid: move somewhere cool, remove extra clothing, drink water and cool the skin; most people improve within 30 minutes.
- Heatstroke: a very high temperature with hot skin, confusion, fast breathing, a seizure or collapse; it can kill.
- Emergency: call 112 for any sign of heatstroke, or if someone is still unwell after 30 minutes of cooling.
Do not book a video appointment if someone who has been in the heat is confused, restless, very drowsy, has hot skin that has stopped sweating, is breathing fast, has a seizure or collapses, or is still unwell after 30 minutes of cooling and fluids. These are signs of heatstroke: call 112, and keep cooling them while you wait.
Can an online doctor help with heat exhaustion?
Partly. Heat exhaustion is treated with first aid where it happens, and most people feel better within 30 minutes of cooling down and drinking. A doctor by video can then check that recovery is on track, look at the conditions and medicines that make heat harder for you, and help you plan the rest of a hot spell or a holiday. Heatstroke is a different matter: it is an emergency, and it needs 112, not a consultation.
How an online consultation helps after heat exhaustion
- Recovery checked: The doctor asks how quickly you improved, how much you are drinking and passing urine, and whether any warning signs remain.
- Dehydration assessed: Thirst, dizziness on standing and dark urine are weighed, and the doctor tells you whether drinking more is enough or you need to be seen.
- Your medicines reviewed: Some medicines and conditions change how the body copes with heat. The doctor reviews yours, and never asks you to stop a medicine without a plan.
- A plan for the hot days ahead: When to go out, how much to drink, and how to adapt walking, sport or sightseeing to the heat.
What the doctor checks in an online heat exhaustion consultation
The consultation follows a fixed order, and the heatstroke signs come first. The doctor asks about:
- Heatstroke signs: confusion, hot dry skin, fainting, a seizure, fast breathing or a racing heart.
- How you responded to cooling: how long it took to feel better, and whether any symptoms remain.
- Fluids: how much you are drinking and passing urine, its colour, and any vomiting or diarrhoea.
- Your health: heart, kidney or lung conditions, diabetes, pregnancy, and any advice to limit your fluids.
- Your medicines and the setting: regular medicines, alcohol, the activity and the temperatures you were exposed to.
Before the call, rest somewhere cool, keep a drink to hand, and take your temperature if you have a thermometer.
Heat exhaustion or heatstroke?
Heat exhaustion happens when the body loses too much water and salt through sweating. Heatstroke happens when the body’s cooling fails and its temperature keeps rising. Heat exhaustion can turn into heatstroke if the person stays in the heat, which is why the first 30 minutes matter.
Swipe sideways to compare →
| Sign | Heat exhaustion | Heatstroke |
|---|---|---|
| Skin | Sweating heavily, pale and clammy | Hot, and may have stopped sweating |
| Temperature | High | Very high |
| Mind | Tired and irritable | Confused, restless, drowsy, or unconscious |
| Breathing and pulse | Usually normal | Fast breathing and a racing heart |
| Other signs | Headache, nausea, cramps, strong thirst | Seizures or collapse |
| After 30 minutes of cooling | Feeling better | Not better: call 112 |
Sunstroke is an older word for heatstroke caused by sun exposure. The danger comes from the heat, not the sun itself, so it can also happen indoors, in a car or during exercise on a cloudy day.
How do you know if it is heatstroke?
In heatstroke, the core body temperature is usually above 40°C, and the brain is affected: confusion, slurred speech, agitation, a seizure or collapse. It comes in two forms. Classic heatstroke builds up in a heatwave, mostly in people over 65, and the skin is often hot and dry. Exertional heatstroke strikes young, healthy people during hard exercise or work in the heat, and they may still be sweating. Heatstroke can also develop without warning, so do not wait for every sign.
What are the stages of heat illness?
Heat illness runs from mild to life-threatening, and heat exhaustion can turn into heatstroke if the person stays in the heat, so act on the early stages:
Swipe sideways to compare →
| Stage | What you notice | What to do |
|---|---|---|
| Heat rash | Clusters of small, red, pimple-like spots on the neck, chest, groin or elbow creases | Stay somewhere cool and dry |
| Heat cramps | Heavy sweating with painful muscle spasms during hard exercise | Stop, move somewhere cool, and drink water or a sports drink; get medical help if they last more than an hour |
| Heat exhaustion | Heavy sweating, pale clammy skin, dizziness, headache, nausea, cramps and strong thirst | First aid; you should feel better within 30 minutes |
| Heatstroke | Temperature usually above 40°C, hot skin, confusion, fast breathing, a seizure or collapse | Call 112 and keep cooling |
Heat exhaustion symptoms
Symptoms often come on during or after activity in hot weather, and they are similar in adults and children:
- tiredness and weakness
- dizziness or feeling faint
- a headache
- feeling sick or being sick
- heavy sweating with pale, clammy skin
- cramps in the arms, legs or stomach
- a high temperature and strong thirst
- irritability
Dark urine, passing less urine than usual and a dry mouth add dehydration to the picture, and they tell you that drinking more is part of the fix.
First aid for heat exhaustion
Act straight away. These four steps are the treatment:
- Move the person to a cool place, out of the sun.
- Remove unnecessary clothing, such as a jacket or socks.
- Give plenty of water to drink. A sports drink or an oral rehydration solution mixed with water also replaces the salt lost in sweat.
- Cool the skin: spray or sponge it with cool water and fan it, and place cold packs wrapped in cloth under the armpits or on the neck.
Stay with the person. They should start to cool down and feel better within 30 minutes. If they do not, or if any sign of heatstroke appears, call 112.
While you wait for help with heatstroke
- Keep cooling: wrap the person in a cool, wet sheet, or fan them and sponge them with cold water.
- If they lose consciousness, put them in the recovery position and tell the emergency operator.
- Check their breathing and pulse, and start CPR if there are no signs of life.
- Do not give drinks to someone who is drowsy, confused or unconscious.
Who is most at risk from the heat?
Anyone can get heat exhaustion in hot weather or during hard exercise, but some people are at higher risk:
- older people, especially those over 65
- people with heart, lung or kidney conditions, or diabetes
- people who live or travel alone, who may not be noticed when they become unwell
- people working or exercising outdoors, including hikers and runners
- visitors from cooler climates who arrive during a heatwave and have not adjusted to the heat
- babies and young children
Some medicines change how the body handles heat or fluids, including water tablets (diuretics), beta blockers, calcium channel blockers, antihistamines, antipsychotics, some antidepressants, lithium and laxatives. Alcohol and stimulant drugs add to the risk. If you take regular medicines, ask the doctor how to manage them in a heatwave rather than stopping them.
Heat in Europe
Europe carries a heavy share of the world’s heat deaths: 36% of an estimated 489,000 heat-related deaths a year worldwide between 2000 and 2019. The 2003 summer heatwave caused about 70,000 deaths in Europe, and an estimated 61,672 people died from heat in Europe in the summer of 2022. Among people over 65, heat-related deaths rose by about 85% between the early 2000s and 2017 to 2021.
How to prevent heat exhaustion on holiday
Most heat illness is preventable. On hot days:
- Stay out of the sun between 11am and 3pm, and plan walking and sightseeing for the cooler early morning and evening.
- Drink water regularly through the day, before you feel thirsty, and more when you are active.
- Wear light-coloured, loose clothing and a hat, and look for shade.
- Avoid drinking a lot of alcohol, and avoid extreme exercise in the heat.
- Spend a few hours each day somewhere cool, such as an air-conditioned museum, shop or room.
- Keep your room cool: close curtains during the day, and open windows at night when it is cooler outside.
- Use a fan only while the air is below 40°C; in hotter air, find air conditioning, set at around 27°C.
- Take cool showers, and never leave anyone in a parked car.
To plan around the heat, see how hot your destination gets in summer in the European Travel Health Index, and check the daily heat and UV scores for European cities in the Climate Health Index.
Which heat exhaustion treatment might the doctor recommend?
Treatment depends on how quickly the symptoms respond to cooling. This is the framework the doctors use, in line with NHS and WHO guidance.
Swipe sideways to compare →
| What you have | Likely first step | Suitable for online care? | When in-person care is needed |
|---|---|---|---|
| Recovered within 30 minutes of cooling | Fluids, rest out of the heat, a plan for the next days | Yes | If symptoms return or new ones appear |
| Still thirsty, dizzy on standing, passing little urine | Steady fluids or oral rehydration solution; review of medicines | Yes | If you cannot keep fluids down |
| Vomiting that stops you drinking | Assessment for fluids through a drip | No | In-person care now |
| Still unwell after 30 minutes of cooling | Emergency assessment | No | Call 112 now |
| Confusion, hot dry skin, seizure or collapse | Heatstroke: emergency cooling and treatment | No | Call 112 now |
Recovering from heat exhaustion and not sure what comes next? A doctor can tell you in one consultation.
See available times →Treatment options for heat exhaustion
What you can do yourself
- Rest somewhere cool for the rest of the day, and take the next day easy.
- Drink regularly in small amounts, and use an oral rehydration solution from the pharmacy if you have been sweating heavily.
- Avoid alcohol and drinks with a lot of caffeine until you have fully recovered.
- Check your urine: pale yellow means you are drinking enough.
Prescription treatment
A prescription is never issued without a consultation. Heat exhaustion is treated with cooling and fluids, and medicine is rarely needed. If you take regular medicines that affect your fluids, the doctor reviews them with you, and never asks you to stop one without a plan. If the doctor prescribes, use the prescription at a pharmacy near you.
What does not help
Fever medicines such as paracetamol do not treat heat illness: cooling does. Waiting to see whether someone who is confused gets better on their own wastes the time that matters most.
Special situations
Heat in pregnancy
Pregnancy makes it harder to stay cool. Rest in the shade, drink regularly and avoid the hottest hours. Feeling faint, a severe headache or reduced baby movements need prompt medical advice.
Heart, kidney or other conditions that limit fluids
If a doctor has told you to limit how much you drink, ask how to adjust this in a heatwave rather than guessing. The balance between too little and too much fluid needs a plan.
Hiking, sport and outdoor work
Start early, carry more water than you think you need, rest in the shade every hour, and stop at the first signs of dizziness or cramps. Heat and dehydration also make altitude sickness harder to recognise in the mountains.
Sunburn and heat rash
Sunburn adds to heat stress and fluid loss, and an itchy, prickly rash in the heat is usually heat rash, which is harmless but uncomfortable. See the sunburn page for burns that blister.
Children
Mobi Doctor consultations are for adults aged 18 and over. A child who is unwell needs a paediatrician or a local doctor in person, and emergency signs in a child mean 112.
When heat exhaustion is treated online, and when you need in-person care
Treated online: advice after heat exhaustion that has responded to cooling, mild dehydration, a review of medicines and conditions that raise your risk, and planning for hot weather or a hot destination.
In-person care: any sign of heatstroke, symptoms that last beyond 30 minutes of cooling, vomiting that stops you drinking, and fainting.
When to get in-person care
Call 112 or go to an emergency department now for:
- confusion, restlessness, drowsiness or loss of consciousness after heat exposure
- hot skin that has stopped sweating, fast breathing or a racing heart
- a seizure or collapse
- anyone still unwell after 30 minutes of rest in a cool place, cooling and fluids
Get medical advice the same day for:
- vomiting that stops you keeping fluids down
- dizziness on standing that does not go away, or passing much less urine than normal
- symptoms that keep coming back over the next days
How Mobi Doctor works
- Book a time that suits you: daily 7am–11pm CEST. You can see a doctor over video, usually within 15 minutes. No subscription, and the exact price is shown before you pay.
- Speak to a licensed doctor about the heat: say how quickly you recovered, how much you are drinking, and which conditions and regular medicines you have.
- Leave with a plan: what to do, what to take and for how long, and which signs mean you should be seen in person. If the doctor prescribes, use the prescription at a pharmacy near you.
No sign-up needed
Not sure it’s heat exhaustion? Tick every symptom you have to see each condition page that mentions it. It finds the right page, not a diagnosis: a doctor gives you that on a video call. If you have an emergency sign listed on this page, call 112 instead.
Tap the body — an area or a point — to browse symptoms anywhere
Similar symptoms, different condition? Dehydration can start the same way. Compare them, or look up any other symptom in the full symptom checker.
Frequently asked questions about heat exhaustion and heatstroke
What is the difference between heat exhaustion and heatstroke?
Heat exhaustion comes from losing too much water and salt through sweating, and it improves with cooling and fluids. Heatstroke happens when the body can no longer control its temperature: the skin is hot, the person becomes confused or collapses, and it is an emergency that needs 112.
What causes heat exhaustion?
Heat exhaustion is caused by losing more water and salt in sweat than you replace while the body works to shed heat, so blood volume falls and the circulation struggles; hot, humid weather, hard exercise, heavy clothing, alcohol, not drinking enough and a hot room or car are the usual triggers. The risk is higher over 65, in babies, in pregnancy, with heart, kidney or lung disease, obesity or diabetes, and with medicines such as diuretics, beta-blockers and some antidepressants.
What is heatstroke?
Heatstroke is the most severe form of heat illness: the body can no longer control its temperature, which rises above 40°C, and the brain and other organs can be damaged. It causes confusion, hot skin, fast breathing, seizures or collapse, and it is an emergency: call 112.
How do you tell if you have heatstroke?
Confusion, slurred speech or agitation after heat exposure are the key signs of heatstroke, with a very high temperature, hot skin that may have stopped sweating, fast breathing, a racing heart, a seizure or collapse. Anyone still unwell after 30 minutes of cooling also needs emergency help: call 112.
How long does heatstroke last?
Heatstroke needs emergency cooling, ideally starting within 30 minutes of the first symptoms, and hospital care, and recovery depends on how quickly cooling starts. Some people have lingering effects for weeks or months, and organ damage can last for years. Sunstroke is the same condition.
How long does heat exhaustion last?
With first aid, most people with heat exhaustion start to feel better within 30 minutes and recover fully within a day or two. Anyone still unwell after 30 minutes of cooling and fluids needs emergency help.
What should I do at home if someone has heat exhaustion?
For heat exhaustion, move them somewhere cool, remove extra clothing, give them water or a rehydration drink, and cool their skin with cool water and a fan. Stay with them, and call 112 if they are not better within 30 minutes or show any sign of heatstroke.
Is sunstroke the same as heatstroke?
Yes. Sunstroke is an older name for heatstroke brought on by the sun. The danger comes from the heat itself, so heatstroke can also happen in a hot room, a car or during exercise without strong sun.
Can you get heat exhaustion indoors?
Yes. A hot room without air conditioning or airflow during a heatwave can cause heat exhaustion, especially in older people and those with long-term conditions. Keep curtains closed in the day and spend some hours somewhere cool.
What should I drink to recover from heat exhaustion?
After heat exhaustion, water is enough for most people. After heavy sweating, a sports drink or an oral rehydration solution also replaces lost salt. Avoid alcohol and drinks with a lot of caffeine until you have recovered.
Can an online doctor help with heat exhaustion?
Yes, once first aid has worked. A doctor by video can check your recovery from heat exhaustion and fluids, review medicines and conditions that raise your risk, and help you plan the hot days ahead. Heatstroke needs 112, not an online consultation.
How can I avoid heat exhaustion on holiday?
To avoid heat exhaustion, avoid the sun between 11am and 3pm, drink regularly, wear light loose clothing and a hat, limit alcohol, and plan walks and sightseeing for the cooler parts of the day. Spend a few hours each day somewhere cool.
- Heat exhaustion and heatstroke, NHS, National Health Service (UK), reviewed 28 May 2026.
- Dehydration, NHS, National Health Service (UK), reviewed 1 May 2026.
- Heat and health: fact sheet, World Health Organization, 31 July 2026.
- Heat stroke, Cleveland Clinic (US), updated 1 October 2024.
- Heat-related illness, CDC, Centers for Disease Control and Prevention (US), accessed 15 October 2026.
This page is for information only and is not a substitute for a medical consultation. Guideline links are provided for transparency; treatment decisions are made with your doctor.
Related conditions
More about heat exhaustion and heatstroke from the Mobi Doctor blog
Heatstroke VS Sunstroke
In recent years, the world has been experiencing increasing temperatures. More people are becoming ill due to extreme he...
Read article → Expert Health AdviceEurope Heatwave Travel Advice
How Can Travellers Stay Safe During a European Heatwave? Travellers can reduce their risk of heat-related illness by st...
Read article → Diet & NutritionExercising In The Heat
Exercising Safely in Hot Weather: Quick Advice Exercising in hot or humid conditions increases the risk of dehydration,...
Read article →Speak to a doctor after heat exhaustion over video, usually within 15 minutes
Licensed doctors · open daily 7am–11pm CEST · exact price before payment
See available times →