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The body can no longer cool itself — here acting fast counts more than any prevention afterwards.
Also known as: heat stroke · sunstroke · heat exhaustion
Open in the tool — with search and all the links →This compilation is for information and replaces neither medical diagnosis nor treatment. If you have symptoms, see a doctor.
In great heat or strong sun the body can overheat. There are two stages. Heat exhaustion is the milder form: weakness, headache, nausea, dizziness and heavy sweating — here quick cooling, rest in the shade and drinking usually help well. Heat stroke is the emergency: body temperature rises dangerously (over 40 °C), the skin is often hot and dry, and confusion, clouded consciousness or seizures appear — this is life-threatening and needs emergency 144 at once, while cooling at the same time. Sunstroke comes from direct sun on the head and neck and causes headache, a red hot head and nausea. Children and older people are especially at risk.
Three additions that make the difference when it counts.
**Dry skin is not a reliable sign.** It applies to the heat stroke that arises at rest during heatwaves — mostly in old people. Someone who has exerted themselves in the heat, by contrast, is often **soaked in sweat** during a heat stroke. Waiting for dry skin is waiting too long; what counts is the **over 40 degrees** and the **changed head**: confusion, change in character, staggering, seizures, unconsciousness.
**Cooling means cooling, not fanning.** Most effective is **immersion in tap water** — the guideline expressly names tap water rather than iced water, because it is available faster. Failing that: spray with water **and** create a draught, plus cold packs at neck, armpits and groins. Cooling happens while the emergency call is running, not afterwards.
**Give nothing to drink while someone is confused or drowsy** — it goes into the lungs. Fluid then comes through a vein.
And one group is missing from the usual list: not only children and old people but also **young, healthy athletes under twenty-five** — there heat stroke accounts for about 2 in 100 sudden deaths. Plus a point rarely stated: **a whole range of medicines lowers heat tolerance** — water tablets, allergy medicines, certain antidepressants, sedatives, beta blockers, calcium antagonists, neuroleptics and thyroid hormones. Whoever takes them belongs among those at risk in a heatwave, young or not.
Out of the heat, lie down, legs up, cool the skin, sip fluids.
Confusion, clouded consciousness or hot dry skin → 144 and keep cooling.
Avoid midday heat and direct sun, cover the head, drink regularly.
Never leave children in a car; keep an eye on older people on hot days.
Drink spread over the day, warm preferred, enough that the urine stays pale.
In the first hours cool several times for 15 to 20 minutes, always with a cloth in between, and elevate.
In heatstroke the core temperature is above forty degrees and consciousness is altered — that is what sets it apart from sunstroke and from exhaustion. The time spent above forty degrees is what decides: under thirty minutes to cooling, the outlook is good. Whole-body ice water cools fastest, about one degree in three to five minutes. Drinking alone does not lower the core temperature.
Fever reducers do not work in heatstroke — they lower a set point raised by the brain, and here it is not raised: the heat comes from outside and from muscle work. Paracetamol and anti-inflammatories can in this situation put extra strain on liver and kidney. What works is cooling from outside, and within minutes: ice water, wet cloths with a draught, cold packs at neck, armpits and groin.
Thirst lags behind the loss, especially with age. Cool the forearms and neck — the vessels lie shallow there. With long exertion something salty belongs with it.
Cross-ventilate at night, windows shut and shaded from outside by day. A fan cools the skin, not the air — above 35 degrees it does little.
Weakness, headache, nausea, dizziness — still sweating; improves on cooling.
Hot skin, >40 °C, confusion or unconsciousness → emergency 144 at once.
Direct sun on head/neck → headache, red hot head, nausea.
Children, older people and the ill overheat faster.
Can derail in both directions: high through loss of water, low through drinking a great deal without salt. Both explain confusion and seizures.
Strongly raised when muscle tissue breaks down — the feared consequence of severe heatstroke and the reason for giving a lot of fluid.
The kidneys are the organ that takes damage fastest in heatstroke. The value steers the treatment.
Makes sure the muscle lets go again after tensing. A lack favours cramps, twitching and inner restlessness — and the blood value reflects the store poorly.
Sets the excitability of muscle and nerve. A low value causes weakness and cramps, a high one is dangerous for the heart rhythm — here one measures rather than guesses.
Sets off the tensing in the muscle in the first place. A low value causes tingling around the mouth and in the fingers and cramping of the hands.
With heavy sweating both are lost together. Drinking only water dilutes the sodium further — with long exertion salt belongs with it.
With heatstroke it is cooling first, not drinks — and anyone not clearly present gets nothing to drink. Afterwards, with heat exhaustion, 0.5–0.7 g sodium per litre replaces what left with the sweat.
Sweat carries away distinctly more sodium than potassium. Pure potassium preparations are rarely needed here and are not harmless with reduced kidney function — fruit and potatoes deliver it more safely.
Effective when deficient; effects on sleep and stress plausible but moderate. Too much causes loose stool.
With heat over days the body adapts: this hormone holds sodium back, and the sweat becomes less salty. That adaptation takes 7–14 days — which is why the first hot days are the most dangerous, not the hottest.
Thirst comes later than the lack of water — in older people distinctly later. This is why in heat one drinks to a plan and not by feeling.
With heavy sweating 0.5–1.5 g of sodium goes per litre of sweat. Drinking only water then dilutes the blood further — under long heat exposure salt is needed alongside.
Alcohol dehydrates and at the same time disturbs temperature regulation. In heatwaves this is one of the most common causes of collapse in the afternoon.
Cooling takes priority over everything else: shade, wet cloths, moving air — and right away.
AWMF 053-052 · S1 · 2025-07 — expired
Hitzebedingte Gesundheitsstörungen in der hausärztlichen Praxis
checked 2026-09 · last looked for a successor 2026-09-20