Hot flashes have several possible causes, but the most common by far is the hormonal shift that happens during menopause and perimenopause. About 75% of women experience these sudden surges of heat at some point during the menopausal transition. However, hormonal changes aren’t the only explanation. Thyroid disorders, medications, anxiety, infections, and certain cancers can all trigger hot flashes or symptoms that feel identical to them.
How Hot Flashes Work in the Brain
Your brain has a built-in thermostat located in the hypothalamus. Under normal conditions, this thermostat operates within a comfort range of about 0.4°C. Small fluctuations in your body or surrounding temperature stay within that range and go unnoticed. Your body doesn’t bother launching a cooling response.
When estrogen levels drop, that comfort range narrows dramatically. A temperature shift that would normally be too small to matter now exceeds the limit, and the brain reacts as though you’re overheating. It triggers a rapid cooling response: blood vessels near the skin dilate, blood flow increases, and sweat glands activate. The result is the familiar sudden flush of heat, redness, and perspiration, often followed by chills as your body overcorrects. This narrowing of the thermoregulatory zone is the most widely accepted explanation for menopausal hot flashes.
Menopause and Perimenopause
The most common cause of hot flashes is the decline in estrogen that begins during perimenopause, sometimes years before periods stop entirely. For 80% of women who get hot flashes, they last two years or less, but a smaller percentage deal with them for much longer. Hot flashes can happen during the day or concentrate at night (often called night sweats), and they tend to peak in frequency during late perimenopause and the first year or two after the final menstrual period.
Surgical menopause, where both ovaries are removed, causes an abrupt drop in estrogen rather than a gradual one. This tends to produce more intense hot flashes than natural menopause because the body has no time to adjust to declining hormone levels.
Medications That Trigger Hot Flashes
Several widely prescribed drugs cause hot flashes as a side effect, particularly those that lower or block sex hormones. Breast cancer treatments are among the most common culprits. Tamoxifen, which blocks estrogen’s effects on breast tissue, frequently causes hot flashes. Aromatase inhibitors, used to treat hormone receptor-positive breast cancer, work by reducing estrogen production throughout the body and commonly cause hot flashes and night sweats as well.
Opioid withdrawal, certain blood pressure medications, and some osteoporosis drugs can also produce flushing episodes. If your hot flashes started or worsened around the time you began a new medication, that timing is worth noting.
Hot Flashes in Men
Hot flashes aren’t exclusive to women. An estimated 60% to 80% of men receiving androgen deprivation therapy for prostate cancer experience them. These treatments work by drastically reducing testosterone, and the mechanism is similar to what happens with estrogen loss in women: the brain’s thermostat becomes hypersensitive. Men with naturally declining testosterone levels can also experience milder hot flashes, though this is less common and less studied.
Thyroid and Other Endocrine Disorders
An overactive thyroid (hyperthyroidism) is one of the more common non-menopausal medical causes of hot flashes and heat intolerance. The thyroid gland controls your metabolic rate, and when it’s producing too much hormone, your body generates excess heat. Other signs that point toward a thyroid problem include a rapid heartbeat, anxiety, tremor, diarrhea, and unexplained weight loss.
Pheochromocytoma, a rare tumor of the adrenal gland, produces surges of adrenaline-like hormones that cause episodic sweating, headaches, a pounding heart, and sudden spikes in blood pressure. Carcinoid tumors, which release hormones into the bloodstream, can cause distinctive flushing episodes along with abdominal cramping and diarrhea. Diabetes can also trigger episodes of sweating when blood sugar drops too low.
Anxiety and Panic Attacks
Stress and anxiety activate the same branch of the nervous system responsible for the “fight or flight” response, which dilates blood vessels and raises your heart rate. The physical sensation can be nearly indistinguishable from a hormonal hot flash. A 2016 study found that people with somatic anxiety, the kind that produces physical symptoms like stomachaches, headaches, and dizziness, had a higher chance of experiencing hot flashes.
Panic attacks are particularly likely to mimic hot flashes because they involve sharp spikes in heart rate and breathing. The relationship also runs in both directions: anxiety can trigger a hot flash, and the sudden, uncomfortable rush of a hot flash can provoke anxiety. For people going through perimenopause who also have an anxiety disorder, the two can reinforce each other in a frustrating cycle.
Infections and Blood Cancers
Night sweats that drench your sheets can sometimes signal an infection or malignancy rather than a hormonal shift. Tuberculosis classically causes night sweats several times per week, along with cough, low-grade fever, and weight loss. HIV infection frequently presents with fever and night sweats, either from the virus itself or from secondary infections that take hold as the immune system weakens.
Lymphoma and leukemia are the cancers most closely associated with drenching night sweats. In these cases, sweats typically come with other warning signs: unexplained weight loss, persistent fatigue, swollen lymph nodes that aren’t related to a recent illness, or recurrent fevers. The key distinction from menopausal hot flashes is the presence of these additional systemic symptoms. Menopausal hot flashes are uncomfortable but don’t come with fever, weight loss, or swollen glands.
Everyday Triggers That Make Hot Flashes Worse
If you’re already prone to hot flashes from any of the causes above, certain everyday habits can lower the threshold for triggering one. Spicy foods are a well-known culprit, but even hot-temperature foods and drinks can set off an episode. Letting your coffee or soup cool to a warm temperature before consuming it can make a noticeable difference.
Caffeine and alcohol both affect blood vessel dilation. Caffeine stimulates the nervous system in ways that can provoke flushing, while alcohol directly widens blood vessels and increases blood flow to the skin. The research on alcohol is mixed, but reducing intake is a straightforward experiment if you’re trying to identify your personal triggers. Warm rooms, heavy blankets, and layered clothing are also common aggravators, especially at night.
How to Tell What’s Causing Yours
Age and context are the biggest clues. Hot flashes in a woman between 40 and 55 with irregular periods are almost certainly related to perimenopause. Hot flashes that started shortly after beginning a new medication point to a drug side effect. Hot flashes accompanied by rapid heartbeat, weight loss, or tremor suggest a thyroid issue worth investigating with a simple blood test.
The features that warrant more urgent evaluation are night sweats combined with unexplained weight loss, persistent fevers, or new lumps. These patterns suggest the sweating may be a symptom of infection or malignancy rather than a hormonal fluctuation. For most people, though, hot flashes trace back to a shift in reproductive hormones, and the pattern of when they started and what else changed at the same time usually tells the story.