Feeling Hot: Why Your Body Feels Hot and What to Do

What feeling hot means

Your brain keeps your core temperature close to 37 °C (98.6 °F) using a thermostat in the hypothalamus. When it senses too much heat, it widens blood vessels in the skin and switches on sweating. That warm, flushed, sweaty sensation is what most people describe as feeling hot.

You can feel hot in two quite different ways:

• With a fever: your thermostat has been reset higher, usually by an infection. A thermometer reads 38 °C (100.4 °F) or more. You often feel cold and shivery first, then hot as the fever peaks.
• Without a fever: your temperature is normal, but blood flow to the skin, sweating or your heat-sensing nerves are turned up. Hot flashes, anxiety, an overactive thyroid and many medicines work this way.

Medical term for feeling hot

The medical term for feeling hot all the time, or being unable to tolerate warm surroundings, is heat intolerance. A sudden wave of heat with redness and sweating is a hot flash (hot flush) or flushing. Pyrexia is the medical word for fever, which is a measured rise in body temperature rather than a feeling.

Feeling hot but no fever: common causes

If your thermometer is normal but your body feels hot inside, these are the usual explanations.

Hot flashes from menopause and perimenopause

Hot flashes affect about three in four women around menopause. A sudden wave of heat spreads over the chest, neck and face, often with redness, sweating and a racing heart, and lasts from 30 seconds to a few minutes. Chills can follow as you cool down. They often start in perimenopause, while periods are still coming but becoming irregular, and can continue for several years after periods stop. Night sweats are the same thing during sleep.

Hot flashes also happen after surgical removal of the ovaries, with some breast cancer treatments, and in men having hormone therapy for prostate cancer. Men can feel hot without a fever too, most often from anxiety, alcohol, medicines or an overactive thyroid, and less often from low testosterone.

Anxiety, stress and panic

Adrenaline raises your heart rate, widens skin blood vessels and triggers sweating, so you feel suddenly hot and clammy. In a panic attack the heat comes with a pounding heart, shaking, breathlessness and a sense of dread, peaks within about 10 minutes and then fades. Ongoing anxiety can leave you feeling warm and sweaty much of the day.

Overactive thyroid (hyperthyroidism)

Too much thyroid hormone speeds up your metabolism so your body makes more heat. People with hyperthyroidism often feel hot all the time, prefer cold rooms and sweat easily. Other clues are weight loss despite a good appetite, a fast or irregular heartbeat, tremor, anxiety, loose stools, lighter periods and, in Graves disease, bulging eyes or a swelling in the neck (goiter). A simple blood test confirms it.

Food, drink and lifestyle

• Spicy food: capsaicin in chili activates heat-sensing nerves, so you feel hot and may sweat on the face.
• Alcohol: widens skin blood vessels and causes flushing. Some people, especially of East Asian descent, flush strongly because they break down alcohol slowly.
• Caffeine: stimulates the nervous system and can make you feel warm and jittery.
• Big meals: digestion produces heat, particularly after high-protein meals.
• Exercise and heavy clothing or bedding: raise heat production faster than you can lose it.

Medicines

Many medicines cause flushing, sweating or heat intolerance. Common ones include:

• antidepressants (SSRIs and SNRIs, which often cause sweating)
• niacin (vitamin B3) and calcium channel blockers for blood pressure
• opioids and some migraine medicines
• thyroid hormone if the dose is too high
• steroids, and hormone treatments such as tamoxifen or treatments that lower estrogen or testosterone
• stimulants used for ADHD

Low blood sugar

In hypoglycemia, the body releases adrenaline to raise blood sugar. You can suddenly feel hot, sweaty, shaky, hungry and irritable. It mainly affects people with diabetes who take insulin or sulfonylureas, but can occasionally follow a sugary meal in people without diabetes.

Pregnancy

Higher progesterone levels, more blood volume and a faster metabolism make many pregnant women feel warmer than usual, especially in the second and third trimesters.

Less common causes

• Multiple sclerosis: heat does not cause MS, but warmth can temporarily worsen symptoms such as blurred vision or weakness.
• Diabetes and nerve damage: can disrupt normal sweating, so some areas overheat while others sweat heavily.
• Carcinoid syndrome: a rare hormone-secreting tumor causing flushing of the face with diarrhea and wheezing.
• Pheochromocytoma: a rare adrenal tumor causing attacks of heat, pounding headache, palpitations and sweating, often with high blood pressure.
• Withdrawal from alcohol, opioids or sedatives: causes sweating, shakiness and feeling hot and cold.

Feeling hot with a fever

If a thermometer shows 38 °C (100.4 °F) or higher, an infection is the most likely cause: a cold or flu, COVID-19, a urinary tract infection or a chest infection. Feeling hot with a fever usually comes with chills, aches and tiredness and settles as the infection clears. See the fever page for home care and when a fever needs a doctor.

Other causes of a raised temperature include inflammatory conditions, some medicines (drug fever), blood clots and, rarely, cancers such as lymphoma, which often cause fevers with drenching night sweats and weight loss.

Overheating from heat illness

When you cannot lose heat fast enough in hot weather or during hard exercise, your core temperature really does rise.

Heat exhaustion can progress to heat stroke, which is life-threatening. Babies, adults over 65, people with heart disease and people taking diuretics, antipsychotics or anticholinergic medicines are at higher risk.

Why do I suddenly feel hot?

Sudden heat that comes and goes usually has a trigger. Matching the pattern to the cause helps.

Feeling hot as a woman

Women report feeling hot more often than men because of hormonal changes across life:

• Before a period: a small rise in body temperature after ovulation, caused by progesterone, makes some women feel warmer in the second half of the cycle.
• Pregnancy and after birth: warmer during pregnancy, and night sweats are common in the weeks after delivery as hormone levels drop.
• Perimenopause and menopause: the most common reason for hot flashes and night sweats from the mid-40s onward.
• Thyroid disease: overactive thyroid is several times more common in women than in men.

When to worry about feeling hot

Most episodes of feeling hot pass on their own. See a doctor if:

• you feel hot all the time for more than a few weeks without an obvious reason
• you also have weight loss, a fast heartbeat, tremor or a neck swelling
• you have repeated fevers or drenching night sweats
• hot flashes are disrupting your sleep, work or mood
• episodes come with headache, palpitations and high blood pressure readings

Seek emergency care for feeling hot with confusion, fainting, chest pain, breathing problems or a very high temperature.

How doctors find the cause

Your doctor will ask whether you have checked your temperature, when the heat happens, how long it lasts, what you were doing, your periods and age, your medicines, alcohol and caffeine use, and other symptoms such as weight change, palpitations or diarrhea. They will check your pulse, blood pressure, temperature, skin and neck.

Common tests include:

• Thyroid function tests (TSH and free T4)
• Blood sugar or HbA1c to check for diabetes
• Complete blood count and inflammation markers if fever or infection is suspected
• Hormone tests in some cases, although menopause is usually diagnosed from age and symptoms alone over 45
• Specialist urine or blood tests if carcinoid syndrome or pheochromocytoma is suspected

How to stop feeling hot

Cool down quickly

• Move to a cooler place, take off a layer and use a fan.
• Drink cool water. Sip it steadily rather than gulping.
• Run cold water over your wrists or put a cool cloth on your neck.
• A lukewarm shower cools better than a very cold one, which can make blood vessels clamp down.

Reduce everyday triggers

• Wear loose, breathable cotton or moisture-wicking clothing in layers.
• Keep your bedroom cool and use light bedding.
• Cut back on alcohol, caffeine and very spicy food if they set you off.
• Try slow breathing (breathe in for 4 seconds, out for 6) when a flash or anxiety surge starts.
• Stay active and keep to a healthy weight, which reduces hot flashes in many women.

Treat the cause

• Hot flashes: hormone therapy is the most effective treatment for most healthy women under 60. Non-hormonal prescription options exist for women who cannot or prefer not to take hormones.
• Overactive thyroid: antithyroid medicines, radioactive iodine or surgery, often with a beta-blocker to calm the heart and heat symptoms at first.
• Anxiety: cognitive behavioral therapy (CBT) and, when needed, medicine.
• Medicine side effects: your doctor may adjust the dose or switch. Do not stop a prescribed medicine without advice.
• Fever: acetaminophen (paracetamol) or ibuprofen, following the label dose. Do not give aspirin to children or teenagers.

Frequently asked questions

Why do I feel hot but have no fever?

Your body can feel hot without a raised temperature when blood flow to the skin increases or your heat-sensing nerves are triggered. Hot flashes, anxiety, an overactive thyroid, alcohol, spicy food, caffeine and medicines such as antidepressants are the most common reasons. If it persists for weeks, ask your doctor about a thyroid test.

Why do I feel hot all the time?

Feeling hot all the time is called heat intolerance. Common causes are an overactive thyroid, menopause, medicines, pregnancy, being overweight and anxiety. If you also have weight loss, a fast heartbeat or tremor, see a doctor for a blood test, because thyroid problems are easy to diagnose and treat.

What is the medical term for feeling hot?

Heat intolerance is the term for feeling uncomfortably hot when others do not. A sudden wave of heat is a hot flash or flushing. Fever, or pyrexia, means your measured body temperature is 38 °C (100.4 °F) or higher.

Why do I suddenly feel hot and sweaty for no reason?

Sudden heat and sweating usually has a hidden trigger: a hot flash, a surge of anxiety, low blood sugar, alcohol or a medicine. Note when it happens and what you were doing. Episodes with chest pain, fainting or breathlessness need emergency care.

Can anxiety make your body feel hot?

Yes. Anxiety releases adrenaline, which speeds up your heart, widens blood vessels in your skin and triggers sweating. You may feel a sudden rush of heat, often with a racing heart, shakiness and tightness in your chest. It passes as the anxiety settles.

Is feeling hot a sign of high blood pressure?

High blood pressure usually causes no symptoms, so feeling hot is rarely due to it alone. Some blood pressure medicines cause flushing, and rare conditions such as pheochromocytoma cause attacks of heat with very high blood pressure. Check your blood pressure if you are concerned.

Can low iron or vitamin deficiency make you feel hot?

Iron deficiency more often makes people feel cold and tired than hot. Niacin (vitamin B3) supplements commonly cause flushing. If you feel hot for no clear reason, a doctor can check your thyroid, blood sugar and blood count together.