Heat-Related Illness Symptoms: When Is It an ER Emergency?

Heat-Related Illness Symptoms: When Is It an ER Emergency?

August 14, 2026
Sean F Isaak's profile picture

Sean F Isaak, MD

Emergency Medicine

Extreme heat, strenuous activity, high humidity and dehydration can escalate and cause heat-related illnesses, such as heatstroke. There are signs you should watch out for to make sure you are taking the proper precautions and aren’t getting overheated.

Early Signs of Heat Illness and Heat Cramps

Heat-related illnesses occur on a spectrum. When your environment is too hot and you’re not cooling off quickly enough, you may develop heat-related symptoms, including:

  • Painful muscle cramps or spasms
  • Heavy sweating
  • Extreme thirst, often caused by losing water and electrolytes through sweating

Heat Exhaustion Symptoms To Watch For

If you start to experience the early symptoms of heat-related illness and can’t or don’t cool off, your symptoms may progress to heat exhaustion. In addition to the above symptoms, you may find your symptoms worsening and showing up in other ways, such as:

  • Fatigue
  • Nausea or vomiting
  • Headache
  • Dizziness and lightheadedness
  • Weakness
  • Elevated temperature
  • Fast heartbeat
  • Persistent cramps

Heatstroke Symptoms: When To Call 911

With heatstroke, your core body temperature becomes very elevated and concerning brain symptoms develop, such as headache, confusion and altered mental status. Heatstroke is a medical emergency and requires prompt treatment to lower the body temperature.

It’s also time to seek medical attention if you feel like you can’t cool down or have concerning symptoms. Most likely, at this point you’d be too impaired to drive. Call 911 immediately.

Heatstroke is rare, but often fatal. When in doubt, take yourself or your loved one to the ER to receive medical care.

Who Is at High Risk for Heat-Related Illnesses?

Age and pre-existing medical conditions make someone more likely to suffer heat illnesses. Infants and young children, as well as adults age 65 and older are at greater risk. Those with significant medical problems, such as heart conditions, should also take more precautions. Certain medications, such as stimulants or anti-depressants, may also increase your risk.

If you’re drinking alcohol, it works against you in two ways. It dehydrates you, and it impairs your judgment. If you’re numb to the signs, you may ignore how much you’re sweating and how you feel. If you plan to drink at a sporting event, outdoor party or other gathering, plan on drinking water and taking shade breaks – even if you don’t feel that you need them.

How To Prevent Heatstroke and Overheating

Prevent any heat-related symptoms from worsening. When you start feeling overheated, act immediately.

  • Stop exercising or engaging in rigorous physical activity.
  • Stay hydrated. Drink water and other fluids before you feel thirsty, and don’t solely rely on your sense of thirst before hydrating. Hydration is not an exact science. If you’re sweating a lot, drink more water and non-caffeinated beverages. Your urine should be light yellow to clear. Drinking excessive caffeine makes you dehydrated, so try and avoid heavy caffeine consumption on overly hot or humid days. Younger children may not be able to verbalize thirst or how thirsty they are, so keep encouraging them to hydrate.
  • Wear appropriate clothing. Clothing should be loose fitting and designed for blocking sun. Certain brands offer long-sleeved lightweight hoodies with a rating of UPF 20+.
  • Cool off. Step into the shade or AC, spray yourself with water, or apply ice or cool, wet washcloths to your skin.

And remember, high humidity prevents sweat from evaporating. The air is already so full of water vapor that it doesn’t allow for much evaporation. Even in temperatures in the 80s, you can struggle to cool down if humidity is high.

This content is not AI generated.