Heat Exhaustion vs. Heat Stroke: How to Tell the Difference

Summer heat can turn dangerous faster than most people expect. Every year, emergency departments across the country, including at Highpoint Health in Middle Tennessee, treat patients for heat-related illness. The two most serious forms are heat exhaustion and heat stroke, and knowing the difference can save a life. One can usually be treated at home with rest, shade, and fluids. The other is a medical emergency that requires a 911 call. Here is how to tell them apart.

What Is Heat-Related Illness?

Heat illness happens when your body takes in more heat than it can release. Sweating is your built-in cooling system, but on hot, humid days, sweat evaporates more slowly and your core temperature can climb. Heat illness moves along a spectrum. It often starts with heat cramps, progresses to heat exhaustion, and can escalate to heat stroke if the warning signs are missed.

Signs of Heat Exhaustion

Heat exhaustion is your body’s warning that it is overheating and running low on water and salt. It often shows up during or shortly after time outdoors, such as yard work, sports practice, or a long afternoon at a summer event. Symptoms usually come on gradually and may include:

• Heavy sweating
• Cool, pale, or clammy skin
• A fast, weak pulse
• Nausea or vomiting
• Muscle cramps
• Dizziness, weakness, or tiredness
• Headache or fainting

Signs of Heat Stroke

Heat stroke happens when the body’s cooling system shuts down. Core temperature can reach 104 degrees Fahrenheit or higher, and organs can begin to suffer damage within minutes. Warning signs include:

• A body temperature of 104 degrees or higher
• Hot, red skin that may feel dry or damp
• A rapid, strong pulse
• Confusion, slurred speech, or agitation
• Loss of consciousness or seizures

Why Sweating Matters

One detail surprises many people: in heat stroke, sweating may slow down or stop even though the person is dangerously hot. That happens because the body has run out of fluid or its temperature controls have failed. Do not assume someone is safe just because their skin feels dry. In young children and older adults, the early signs can also be subtle, such as unusual fussiness, sleepiness, or withdrawal, so watch behavior as closely as symptoms.

The Fastest Way to Tell the Difference

When someone struggles in the heat, ask two questions. First, how does their skin feel? Cool and sweaty points toward heat exhaustion, while hot and flushed points toward heat stroke. Second, are they thinking clearly? A person with heat exhaustion usually feels awful but can still answer questions. Confusion is the single most important red flag. If someone who has been in the heat seems disoriented, is not making sense, or passes out, treat it as heat stroke and call 911.

What to Do for Heat Exhaustion

Most cases of heat exhaustion improve with quick action:

• Move to a cool, shaded, or air-conditioned space
• Loosen or remove extra clothing
• Sip cool water or a sports drink slowly
• Apply cool, wet cloths to the skin or take a cool shower
• Rest with the legs slightly raised

When to Call 911

Call 911 right away if you see any signs of heat stroke, if symptoms of heat exhaustion last longer than an hour, or if vomiting keeps the person from holding down fluids. While you wait for help, move the person to a cooler spot and lower their temperature with cool cloths, a fan, or a cool bath. Do not give a confused or unconscious person anything to drink, and do not leave them alone. Minutes matter, and the cooling you start before the ambulance arrives can make a real difference in how well someone recovers.

If you have questions about heat safety or need care after a heat-related illness, the team at Highpoint Health in Middle Tennessee is here to help. Find a provider at Highpoint Health today.

This article is for general education and is not a substitute for professional medical advice.