New Delhi: As summer temperatures climb across Indian states, heat-related illnesses are becoming a serious public health concern rather than just a seasonal
inconvenience. Heatstroke is the most dangerous form of heat illness because it develops when the body can no longer regulate its temperature and the core temperature rises above 40 degrees Celsius. This is a medical emergency that can affect the brain, heart, kidneys and liver within a short span of time, especially if the person remains exposed to heat or physical exertion without cooling and hydration.
Dr Bhanu Mishra, Consultant Nephrologist, Fortis Hospital, Shalimar Bagh, points out that heatstroke is not simply about “feeling too hot” but about the body entering a dangerous state of temperature dysregulation with the potential for multi-organ injury, including acute kidney strain caused by dehydration and reduced blood flow to the kidneys. In a season when many people ignore early warning signs such as headache, dizziness, nausea and weakness, understanding when heat exhaustion is progressing to heatstroke can make the difference between timely treatment and a life-threatening emergency.
What is heatstroke and why is it so dangerous?
Heatstroke is a severe heat-related emergency that happens when the body’s natural cooling system fails and the core temperature rises to 40 degrees Celsius or above. It may develop after prolonged exposure to high temperatures, humid weather, poor ventilation, or physical exertion in extreme heat, and unlike heat exhaustion, it can quickly lead to organ dysfunction if not treated immediately.
“Heatstroke should never be dismissed as ordinary summer fatigue. Once the body stops coping with the heat load, damage can begin rapidly, and several organs may come under stress at the same time,” says Dr Bhanu Mishra, Consultant Nephrologist, Fortis Hospital, Shalimar Bagh.
The brain is particularly sensitive to rising body temperature, which is why confusion, altered behaviour, agitation, seizures and even coma can occur in severe cases. At the same time, dehydration and circulatory stress can burden the heart, while reduced blood flow to the kidneys may trigger acute kidney injury, a point of special concern in patients who already have kidney disease, diabetes or hypertension.
Common heatstroke symptoms
The most important warning sign is a very high body temperature, usually above 40 degrees Celsius, along with a change in mental status. A person may appear confused, dizzy, disoriented, irritable or unusually drowsy, and in more severe situations may develop seizures, collapse or lose consciousness.
Other common heatstroke symptoms include hot skin, rapid heartbeat, fast breathing, headache, nausea, vomiting, weakness and loss of coordination. In some cases the skin may be hot and dry, while in exertional heatstroke it may remain sweaty because the body is still attempting to cool itself under intense physical stress.
“Many people wait too long because they assume dizziness, vomiting or a racing pulse will settle on their own. But when these symptoms appear with high body temperature or confusion, urgent medical assessment is essential,” says Dr Mishra.
How heatstroke affects the kidneys and other organs
Heatstroke is especially dangerous because it does not stay limited to one system of the body. Once severe overheating sets in, blood circulation becomes strained, dehydration worsens, and vital organs may begin to suffer from reduced oxygen and blood supply.
For the kidneys, this can be particularly serious. Dehydration reduces renal perfusion, meaning the kidneys receive less blood flow, and this may lead to acute kidney injury. In severe cases, muscle breakdown associated with extreme heat can release harmful substances into the bloodstream, adding further stress to the kidneys.
“From a nephrology perspective, heatstroke is dangerous because fluid loss and reduced perfusion can place sudden stress on the kidneys. Patients with existing kidney problems must be especially cautious during extreme heat,” says Dr Bhanu Mishra.
The liver may also be affected because of metabolic disruption and heat-related cellular injury, while the heart may respond to dehydration and overheating with a rapid or irregular heartbeat. This is why doctors treat heatstroke as a whole-body emergency rather than a simple temperature problem.
Immediate first aid for heatstroke
If heatstroke is suspected, immediate cooling must begin while emergency medical help is arranged. The person should be moved at once to a cool, shaded or air-conditioned place, and excess clothing should be removed to help the body lose heat more quickly.
Cooling measures may include pouring cool water over the skin, applying cold wet towels, or placing ice packs over the back of the neck, underarms and groin, where large blood vessels are close to the surface. If the person is fully conscious and able to swallow, small sips of water or oral rehydration fluids may be given, but unconscious or confused patients should not be forced to drink because of the risk of choking.
“First aid should focus on rapid cooling and urgent transfer to hospital. Families should not wait for symptoms to settle at home if the person is confused, fainting, or running a very high temperature,” says Dr Mishra.
According to the NHS, heatstroke is an emergency if someone remains unwell after cooling attempts, or develops hot skin, a fast heartbeat, confusion, seizures or loss of consciousness. Delaying treatment increases the risk of permanent organ damage and can be fatal.
Who is most at risk during a heatwave?
While anyone can develop heatstroke, some groups face a higher risk during very hot weather. These include older adults, young children, outdoor workers, athletes, people with chronic kidney disease, heart disease or diabetes, and those living in poorly ventilated spaces without effective cooling.
People who spend long hours commuting, working outdoors or exercising in direct sun should be especially careful about hydration, rest breaks and avoiding peak afternoon heat. The risk also rises when humidity is high because sweat does not evaporate as efficiently, making it harder for the body to cool itself.
How to prevent heatstroke in daily life
Prevention starts with limiting exposure to extreme heat, especially during the hottest part of the day. Wearing loose, light-coloured clothing, drinking fluids regularly, taking breaks in shaded or cool places, and avoiding strenuous activity in peak afternoon hours can significantly reduce the risk.
Homes, offices and schools should also be better prepared during heatwaves, particularly for children, the elderly and people with chronic illnesses. Even simple steps such as checking on vulnerable family members, carrying water while travelling, and recognising early symptoms of heat exhaustion can help prevent a medical emergency.
“Prevention is always better than emergency treatment. In hot weather, people must take dehydration seriously, recognise warning signs early, and seek prompt care before heat illness progresses to heatstroke,” says Dr Bhanu Mishra.
Heatstroke is a medical emergency that demands fast recognition, rapid cooling and immediate professional care. With temperatures rising sharply during Indian summers, awareness of heatstroke symptoms, first aid, prevention and the risk of kidney injury is essential for every household.
