Heat stroke is a life-threatening emergency that requires immediate cooling and a call to 911. The single most important thing you can do is lower the person’s body temperature as fast as possible while waiting for paramedics. Every minute of delay increases the risk of organ damage, so speed matters more than perfection.
Recognize Heat Stroke Before You Act
Heat stroke and heat exhaustion share symptoms like nausea, dizziness, headache, and fatigue, but one critical difference separates them: brain function. A person with heat stroke will show signs of neurological disruption. They may be confused, slurring words, stumbling, acting delirious, or seizing. Some lose consciousness entirely. Core body temperature is typically above 104°F (40°C), though it can sometimes be slightly lower.
If someone has been in the heat and starts acting confused or disoriented, treat it as heat stroke. You don’t need a thermometer to act. Altered mental status is the defining sign, and waiting for confirmation wastes time.
Cool the Person Immediately
Rapid cooling is the most effective intervention you can provide. The goal is to get the core body temperature down before heat damages the brain, liver, kidneys, and other organs. Tissue injury worsens with both the degree and duration of overheating, so starting within the first few minutes dramatically improves outcomes.
Cold water immersion is the gold standard. If you have access to a bathtub, kiddie pool, horse trough, or any container large enough, fill it with cold water and ice and submerge the person up to their neck. Cold water immersion cools the body at a rate of roughly 0.13°C to 0.35°C per minute and produces the highest survival rates in studies of exertional heat stroke. Keep their head above water and monitor them constantly.
If immersion isn’t possible, use the next best options:
- Ice-soaked towels: Soak towels in ice water and drape them over the person’s body, rotating them frequently as they warm up. Continually rotating ice-soaked towels can cool at about 0.11°C per minute.
- Ice packs on key areas: Place ice packs on the neck, armpits, groin, and torso. These areas have large blood vessels close to the skin, making them the most effective spots for lowering core temperature.
- Spray and fan: Spray or sponge the skin with cool water while fanning aggressively. The evaporation pulls heat from the body.
Do all of this while waiting for emergency services. Don’t stop cooling efforts until paramedics take over.
What Not to Do
Do not give the person Tylenol (acetaminophen), aspirin, or ibuprofen. These medications work by resetting the brain’s temperature set point during fevers caused by infection. Heat stroke isn’t a fever. The brain’s thermostat is functioning normally but has been overwhelmed by external heat or exertion. Antipyretics won’t help, and they can actively cause harm. Heat stroke often stresses the liver and kidneys, and these medications can worsen that damage.
Do not give fluids by mouth if the person is confused, drowsy, or unconscious. Someone with altered mental status can choke or inhale liquid into their lungs. If the person is alert enough to drink on their own, small sips of cool water are fine, but cooling the body takes priority over hydration. Paramedics can provide IV fluids once they arrive.
If the person is unconscious, roll them onto their side to keep the airway clear in case they vomit.
Why Cooling Speed Matters
Heat stroke triggers a cascade of damage throughout the body. The extreme temperature directly injures cells while simultaneously causing an intense inflammatory response. In one study of heat stroke patients, more than three-quarters developed dysfunction in multiple organ systems. Respiratory failure was the most common complication. Liver damage, kidney injury, and muscle breakdown were also strongly associated with worse outcomes.
The severity of this damage is directly tied to how long the body stays overheated. There is no established “safe window,” which is exactly why the medical guidance is simply to cool as aggressively and quickly as you can. Researchers have not identified a specific temperature where you should stop cooling before medical professionals arrive, so keep going until help takes over.
Know Who Is at Higher Risk
Some people are more vulnerable to heat stroke because their bodies can’t regulate temperature as efficiently. Older adults, young children, and people with chronic illnesses are well-known risk groups. But medications are an underappreciated factor that significantly raises risk.
Several common drug classes interfere with the body’s cooling system. Diuretics (often prescribed for blood pressure) cause fluid loss and electrolyte imbalances. Beta blockers reduce the ability to increase blood flow to the skin and decrease sweating. Antipsychotics and anticholinergic medications impair both sweating and the brain’s temperature regulation. Antidepressants, including SSRIs, SNRIs, and tricyclics, alter sweating in different ways. Even common antihistamines like diphenhydramine (Benadryl) can decrease sweating and impair cooling.
Lithium, a mood stabilizer, carries particular risk because dehydration from heat can push blood levels of the drug into a toxic range. If you’re helping someone who takes any of these medications, be especially vigilant on hot days and mention the medications to paramedics when they arrive.
What Happens at the Hospital
Once emergency responders arrive, they continue aggressive cooling and begin IV fluids to support blood pressure and organ function. If the person is having seizures, those are treated with sedatives. Someone who has lost the ability to protect their own airway may need a breathing tube.
Hospital stays for heat stroke often involve the intensive care unit. Providers monitor the brain, kidneys, liver, and lungs for signs of ongoing damage. How long someone stays depends on the severity and how quickly cooling was started.
Recovery After Heat Stroke
Heat stroke is not something people simply bounce back from. Some recover fully within days, but others experience lingering effects for weeks or months. These can include difficulty coordinating movements, slurred speech, and trouble forming new memories. In more severe cases, organ function can remain impaired for years, raising the risk of other health problems down the line.
People who have had heat stroke are also more sensitive to heat afterward. Their body’s thermoregulation may not work as reliably as it did before, meaning future heat exposure carries greater risk than it would for someone who has never experienced heat stroke.