There are many reasons why someone might feel hot but have no fever. Environmental and lifestyle factors, medications, age, hormones, and emotional state all have an impact. In some cases, feeling continuously hot may signal an underlying health condition.
Depending on the cause, a person who feels hot may sweat excessively or not sweat at all. They may look hot, with flushed or irritated skin, or their skin may look unchanged.
In this article, we look at 13 possible causes for feeling hot without a fever, treatment options, and when to see a doctor.
A person can check that they do not have a fever by using a thermometer to measure their body temperature. A digital thermometer is the best option as glass ones can be dangerous.
The Centers for Disease Control and Prevention (CDC) recommend that people measure their temperature when they are not taking fever-reducing medications, such as ibuprofen or acetaminophen (Tylenol).
If an adult’s body temperature is 100.4°F (38°C) or higher, they have a fever. However, if their body temperature is normal, at 98.6°F (37°C), then they do not have a fever.
A child will have a fever if their temperature is 99.5°F (37.5°C).
Many lifestyle and environmental factors can make a person feel hot but not produce a temperature. Factors include:
Heat-related illness
Hot or humid weather is taxing for the body and may affect some people more than others. In hot weather, a person might feel irritable, tired, or find it difficult to concentrate.
In some cases, extreme temperatures or prolonged exposure to the sun can cause heat-related health conditions, such as sunburn, heat exhaustion, and less commonly, heatstroke.
Sunburn occurs when the sun damages the skin, causing it to feel hot and sore. Heat exhaustion occurs when a person loses too much water and salt through sweating. According to the CDC, symptoms of heat exhaustion include:
- heavy sweating
- cold, clammy skin
- nausea or vomiting
- tiredness or weakness
- a headache
- dizziness
- muscle weakness or cramping
Children with heat exhaustion may be excessively tired, thirsty, and have cool, clammy skin.
A person with heat exhaustion should cool down, drink fluids, and stop all physical activity until they feel better. If a person does not cool down or get better within 1 hour, they should seek medical help immediately.
Untreated heat exhaustion can turn into heatstroke, which can be life threatening. Symptoms include confusion, skin that is hot, dry, or changes color, fainting, or unconsciousness. If a person has signs of heatstroke, call 911 right away.
Learn more about the differences between heat exhaustion and heatstroke.
Exercise or strenuous activity
Exercising or carrying out physical tasks can increase a person’s body heat, particularly if they:
- are not used to exercising regularly
- exercise or carry out physical tasks in hot or humid environments
- overexert themselves
The CDC state that athletes who train in hot weather to look out for the signs of heat-related illnesses and to stop training if they feel weak or faint.
Avoiding exercise at the hottest times of the day, drinking more water, and pacing may help people avoid becoming too hot during exercise.
Food and drink
Certain foods and drinks can make people feel hotter than usual. These include:
- alcohol
- caffeine
- spicy food
- food and beverages with a high temperature
People may feel extra heat in their skin or sweat more than usual, during, and after consuming these foods.
Clothing
Tight, restrictive, or dark clothing may increase body heat and prevent air circulation around the skin. Synthetic fibers may also trap heat and prevent sweat from evaporating. This can cause excessive warmth and increased sweating.
A range of conditions and disorders can also cause someone to feel hot. These include:
Anxiety
When a person feels stressed or anxious, they may experience physical symptoms, including feeling hot and sweaty. This happens during the “fight or flight” response, which increases the person’s heart rate and blood supply to their muscles.
A person who is feeling anxious or stressed may also notice:
- increased heart rate
- heart palpitations
- tense muscles
- rapid breathing
Learn more about how anxiety affects the body.
Hyperthyroidism
Hyperthyroidism occurs when a person’s thyroid gland becomes overactive and makes too many thyroid hormones. Thyroid hormones affect how the body uses energy.
People with hyperthyroidism often experience heat intolerance, along with other symptoms such as:
- shaky hands
- a rapid or irregular heartbeat
- diarrhea or frequent bowel movements
- difficulty sleeping
- fatigue
Learn more about hyperthyroidism.
Anhidrosis
Sweating is how the body keeps cool. Anhidrosis describes the inability to sweat. This symptom can affect a small or large area of the body. It may be due to an underlying condition, a medication, or blocked or injured sweat glands.
If someone cannot sweat at all, or cannot sweat across a large area of their body, this could be dangerous. A person with this symptom should speak to a doctor.
Diabetes
According to the International Diabetes Federation, people with diabetes may feel more sensitive to the heat than others. This happens for several reasons:
- Dehydration: People with diabetes become dehydrated more quickly during hot weather. Not drinking enough liquids can also raise blood glucose levels, which causes a person to urinate more. This exacerbates dehydration further.
- Complications: Diabetes can cause complications that damage the blood vessels and nerves, which, in turn, may affect a person’s sweat glands. This may mean a person sweats less, making it more difficult for them to stay cool.
According to the CDC, symptoms of diabetes include:
- frequent urination, especially at night
- feeling very thirsty and hungry
- blurry vision
- tingling in hands or feet
- fatigue
- unintentional weight loss
People may feel hot for a variety of other reasons, including:
Pregnancy and menstrual cycles
According to the National Health Service in the United Kingdom, it is relatively common for pregnant women to feel hotter than usual. This occurs due to hormonal changes, which increase blood supply to the skin’s surface.
Pregnant women may also sweat more. It is common for temperature to rise during the ovulation stage of the menstrual cycle.
Menopause and perimenopause
Females may experience hot flashes during, before, and after the menopause. According to the National Institute on Aging (NIA), hot flashes occur due to changing estrogen levels. Hot flashes may last anywhere from 30 seconds to 10 minutes. Other symptoms of a hot flash include:
- flushed skin on the face and neck
- excessive sweating
- night sweats, which may disrupt sleep
- feeling cold or shivery afterward
Learn more about recognizing the signs of menopause.
Medications
The International Hyperhidrosis Society list a wide range of medications that can cause heat or sweating as a side effect. Medications that might cause a person to feel hot include:
- analgesics, such as naproxen (Aleve) and tramadol
- cardiovascular drugs, such as amlodipine and losartan
- hormonal drugs, such as thyroid medication and testosterone
- gastrointestinal drugs, such as omeprazole or atropine
- skin treatments, such as lidocaine or isotretinoin
- psychiatric drugs, such as tranquilizers and fluoxetine (Prozac)
- some antibiotics and antiviral drugs
If a person thinks that their medication might be causing side effects, they can speak to their doctor to discuss their options.
The treatment for feeling hot without a fever depends on the underlying cause.
People who feel hot due to environmental or lifestyle factors, such as sun exposure, may feel better if they adjust their daily routines. The CDC recommend:
- wearing lightweight, pale, loose-fitting clothing
- staying in air-conditioned spaces
- taking a cool shower or bath
- drinking plenty of fluids and replacing electrolytes lost through sweat
- avoiding spicy foods, caffeine, and alcohol
These strategies may also help pregnant women and those who are experiencing hot flashes.
People who feel hot due to anxiety or stress may also benefit from relaxation techniques that calm the nervous system.
These include deep breathing, yoga, and tai chi. Stress can exacerbate hot flashes, so these techniques may also help people in perimenopause or menopause, according to the NIA.
A person experiencing frequent anxious thoughts may find a form of therapy, such as cognitive behavioral therapy (CBT), helpful for reducing the physical symptoms of anxiety.
However, if these strategies do not help, they may have a condition that requires medical treatment.
If someone frequently or continuously feels hot with no fever, they should see their doctor. A doctor may need to perform tests, such as blood or urine tests, to diagnose the underlying cause.
If someone has symptoms of heat exhaustion that do not improve within an hour or the symptoms of heatstroke, they should seek emergency help.
People may feel hot without a fever for many reasons. Some causes may be temporary and easy to identify, such as eating spicy foods, a humid environment, or stress and anxiety.
However, some people may feel hot frequently for no apparent reason, which could be a symptom of an underlying condition. If people are unsure why they are feeling hot with no fever, they can see their doctor.