What Is Heat Intolerance?

Medically Reviewed by Neha Pathak, MD on July 17, 2023
3 min read

Heat intolerance is when you feel too warm in temperatures that other people find comfortable. When this happens, your body can't control its balance between cold and hot. It tends to develop slowly and last for a long period. But in some cases, it could show up instantly -- especially if it's related to a serious condition.

The inability to regulate your body temperature can be related to a variety of illnesses or be a side effect of certain medications.


The symptoms of heat intolerance can be different for each person. But the common signs of this issue include:

  • Headaches
  • A fast heartbeat
  • Nausea or vomiting
  • Intense fatigue
  • Sweating more than normal or not at all
  • Muscle cramps
  • Weakness
  • Changes in your mood

Heat intolerance can be caused by many things. Tell your doctor if you notice this symptom so they can help find the cause. 

Conditions that can cause heat intolerance. You may develop this symptom if you have an anxiety disorder, if you're in menopause, or if you have thyrotoxicosis (when your thyroid gland makes too much thyroid hormone) from any condition, like hyperthyroidism. 

Other issues and conditions can make you more likely to have heat intolerance. These include:

  • Graves' disease
  • Multiple sclerosis
  • Obesity
  • Heart disease
  • Mental illnesses
  • Diabetes
  • High blood pressure
  • A lower level of physical fitness

Medications that can cause heat intolerance. Different drugs can also lead to this symptom. They include:

  • Amphetamines and other stimulants (like drugs that lessen your appetite)
  • Caffeine
  • Antibiotics
  • Diabetes drugs
  • Antidepressants
  • Blood pressure drugs
  • Antipsychotics
  • Allergy medications (antihistamines or decongestants)
  • Pain relievers
  • Overactive bladder medications

Some legal and Illegal drugs (like opioids, cocaine, or methamphetamines) and alcohol use can also lead to heat intolerance.

Your age might also affect how likely you are to develop heat intolerance. The CDC says that people over 65 are more likely to have heat-related health issues. This is because if you are older, you don't adjust to quick changes in the temperature as well as younger people do. Similarly, older people are more likely to have a chronic condition or take a medication that may affect their body's ability to control temperature.

To diagnose heat intolerance and discover the underlying issue, your doctor will first look at your medical history and do a physical exam.

They may also ask you about your symptoms, if heat intolerance has happened before, when it tends to get worse, and other questions.

Your doctor might want to run tests as well. These might include:

  • Blood studies
  • Thyroid studies (TSH, T3, or free T4)

Treatment for heat intolerance will depend on the cause of your symptom.

Once your doctor figures out why you have heat intolerance, they'll be able to give you advice on how to improve the symptom.

Heat intolerance can lead to issues like heat stroke, which happens when your core body temperature is 104 degrees Fahrenheit or higher. This can be life-threatening.

If this happens, you need to get medical care right away. If you don't treat heat stroke, it can lead to permanent damage in your brain or other organs, which could lead to death.


You can avoid heat-related issues at home with these tips:

  • Keep the temperature indoors at a comfortable level
  • Drink a lot of fluids
  • Don't overdo your time outside when it's hot and humid

You and your employer can also work to avoid heat intolerance at work. Your employer can measure your body's responses to heat to check if your heat stress is too high. Physiologic monitoring may help employees measure their:

  • Heart rate
  • Skin temperature
  • Core body temperature
  • Weight changes from sweating

These values can help an employer understand if their employees are at risk for issues related to heat intolerance.