February 28, 2025

What Is Heat Stroke?

This content has been reviewed and approved by Amy Porter MSN, RN, SCRN

Heat stroke is a life-threatening medical condition where the body overheats and its cooling functions stop working. It often occurs when a person participates in strenuous activities (as determined by their age, fitness level, etc.) in high temperatures for too long.

However, it can also occur without physical exertion, like when you’re outdoors in extreme heat or sitting in an enclosed vehicle on a hot day. Both exertional and non-exertional heat stroke develop when a person’s body temperature rises to 104 degrees Fahrenheit or higher.

Heat stroke requires emergency medical intervention to prevent damage to the brain, heart, kidneys and muscles.

Heat Stroke Symptoms

Heat stroke (sometimes written as heatstroke and also called sunstroke) symptoms include:

Core body temperature of 104 degrees Fahrenheit or higher
Changes in sweating pattern, such as sweating profusely or not at all
Flushed (red) or pale skin
Headache
Nausea and vomiting
Weakness
Fainting
Rapid, shallow breathing
Elevated heart rate
Low blood pressure
Blurred vision
Changes in mental state and behavior, including confusion, agitation, delirium and irritation
Slurred speech
Seizure or coma

The changes in mental state can be especially problematic, as they can cause you not to understand that you’re experiencing a medical crisis. The changes can also cause someone you are with who is experiencing heat stroke to insist they feel fine.

Heat Stroke Risk Factors

You’re more likely to experience heat stroke if you have one or more of the following risk factors:

You work outdoors and have a physically demanding job.
You live in a hot climate with insufficient cooling in your home.
You’re over 65 or pregnant.
You are dehydrated.
You push your body too hard at the encouragement of others like family, friends or sports coaches.
You take medications or use substances that increase your risk of dehydration, reduce how much you sweat or elevate your metabolism and heat production.

Heat Stroke Complications

Heat stroke can lead to severe health problems, including:

Muscle breakdown that releases toxins into your blood
Disruption of brain activity
Reduced oxygen flow to organs
Damage to major organs, including the lungs, liver, kidneys and heart

If heat stroke is left untreated, it can be fatal.

Heat Stroke Diagnosis and Treatment

If you think you or someone you are with is experiencing heat stroke, it is critical to get immediate medical attention. Doctors diagnose heat stroke by asking about your symptoms, performing a physical exam and checking your core temperature (typically with a rectal thermometer). They might also order blood tests, urine tests, electrocardiograms or chest X-rays to check for complications.

Heat stroke treatment focuses on lowering your body temperature as quickly as possible using cold water immersion, ice packs, cooling blankets, intravenous fluids and other means. Care teams also take steps as needed to address complications.

First Aid for Heat Stroke Diagnosis

While waiting for medical attention for someone with heat stroke, you can help lower their body temperature by:

Moving them out of the sun or to a cooler spot
Pouring cool water over their skin and fanning them
Soaking a towel in ice water and applying it to their skin (covering as much of their skin as possible)
Applying ice or cold packs to their armpits and neck

Be aware that you should not give a person with heat stroke fever-reducing medication. You also should not give them anything to drink, as their condition makes them susceptible to inhaling fluids accidentally, which can cause additional medical problems.

Stroke vs. Heat Stroke

While some of their symptoms are similar, stroke (bleeding or a blood clot in the brain) and heat stroke are different conditions with different causes and treatments. However, heat stroke can increase your risk of having a stroke.

Talk With Your Baptist Health Doctor About Heat Stroke

If you have questions about heat stroke or your risk of experiencing it, your doctor can answer them. They can also share tips for avoiding heat stroke, like: