Hot flashes in perimenopause

Hot flashes are the signature symptom of the menopause transition: a sudden wave of heat in the chest, neck and face, often with sweating and a flushed look, lasting one to five minutes. They affect up to 80% of women at some point in the transition, and they often begin in perimenopause, while periods are still happening. They are not dangerous, but they are disruptive, and there are more effective treatments than most women are offered.

What a hot flash is

A hot flash is your body’s heat-loss response firing when it does not need to. Blood vessels in the skin dilate, you sweat, your heart rate rises briefly, and you may feel chilled afterward as the sweat evaporates. When the same thing happens during sleep it is called a night sweat; together they are known as vasomotor symptoms.

Episodes vary enormously. Some women have a few mild flushes a week; others have more than a dozen a day, with drenching sweats at night. Many describe a short warning sensation, a sense of pressure or unease, a few seconds before the heat arrives.

Why hot flashes happen in perimenopause

Your core body temperature is held within a narrow band by a thermostat in the hypothalamus. Above the band you sweat; below it you shiver. In women who have hot flashes, that comfort zone has become very narrow, so a small rise in core temperature that would once have gone unnoticed now trips the full cooling response.

Estrogen is part of why the zone narrows. During perimenopause estrogen does not simply decline; it swings, sometimes higher than before, sometimes much lower, as the ovaries respond erratically to signals from the brain. Those swings appear to destabilize the thermostat. A group of neurons in the hypothalamus that produce a signaling chemical called neurokinin B become overactive when estrogen falls, and they sit right next to the temperature-control center. That discovery is what led to fezolinetant, the first drug designed to block that pathway.

This also explains why hot flashes can start before your periods become irregular and why they can continue for years after your last period: the brain’s thermostat takes time to recalibrate.

How long they last

The best US data come from the Study of Women’s Health Across the Nation (SWAN), which enrolled 3,302 women at seven sites and followed them for up to 17 years. Among women with frequent hot flashes, the median total duration was 7.4 years. Women whose hot flashes began while they were premenopausal or in early perimenopause had the longest course, a median of more than 11.8 years, and Black women reported the longest durations of any group, a median of 10.1 years. After the final menstrual period, frequent hot flashes persisted for a median of 4.5 years.

For more on where you are in the transition, see what perimenopause is.

What else can cause flushing and sweating

Hot flashes in a woman in her 40s with changing periods are almost always perimenopausal. Still, a few other causes are worth keeping in mind, especially if the pattern is unusual or your periods are unchanged:

• Overactive thyroid. Heat intolerance, sweating, a racing or irregular heartbeat, weight loss despite a good appetite and shaky hands point toward hyperthyroidism, which is more common in women. A simple blood test settles it.
• Medications. Some antidepressants, tamoxifen and aromatase inhibitors, opioids and certain blood pressure drugs can cause flushing or sweating.
• Alcohol, which widens blood vessels and worsens both hot flashes and night sweats.
• Low blood sugar, infections with fever and, rarely, hormone-secreting tumors. These usually come with other symptoms and would not be a clinician’s first thought in a typical perimenopausal picture.
• Anxiety and panic, which can produce heat, sweating and a pounding heart, and which also become more common during the transition.

If you want a structured way to lay out your symptoms before a visit, try the symptom check.

What helps, ranked by evidence

The Menopause Society’s 2023 nonhormone therapy position statement graded every option by the strength of evidence. Combined with its 2022 hormone therapy statement, it gives a clear hierarchy.

Hormone therapy: the most effective treatment

Systemic estrogen, with a progestogen if you have a uterus, remains the most effective treatment for hot flashes. The Menopause Society concludes that for women under 60 or within 10 years of their final period who have no contraindications, the balance of benefit and risk is favorable for treating bothersome hot flashes. Contraindications include a history of estrogen-sensitive cancer, blood clots, stroke or heart disease. During perimenopause, when periods are still occurring, clinicians sometimes use a low-dose combined contraceptive instead, which also regulates bleeding.

Nonhormonal prescriptions with Level I evidence

• Fezolinetant (Veozah), approved by the FDA in May 2023, blocks the neurokinin 3 receptor in the brain’s temperature center. It is taken once a day. The FDA has since added a boxed warning for rare but serious liver injury, with liver blood tests required before starting and at intervals during the first nine months.
• SSRIs and SNRIs. Low-dose paroxetine (7.5 mg) is FDA-approved for hot flashes; escitalopram, citalopram, venlafaxine and desvenlafaxine have also reduced hot flashes in large trials. Reductions in hot flash frequency in trials ranged from roughly 25% to 69%. These are a sensible choice when low mood or anxiety travel with the flashes.
• Gabapentin, typically 300 mg three times a day, reduces frequency and severity. Drowsiness and dizziness in the first week are common and usually fade; weighting the dose toward bedtime helps when night sweats are the main problem.
• Oxybutynin, a bladder medication, has Level I to II evidence. Dry mouth is the usual limitation.

Mind-body therapies with Level I evidence

• Cognitive behavioral therapy (CBT) designed for menopause reduces how much hot flashes bother you, even when the number of flashes changes less. It carries Level I evidence.
• Clinical hypnosis has also shown benefit in randomized trials and carries the same grade.

Lifestyle

Only weight loss is recommended for hot flashes (Level II to III evidence), for women who carry extra weight. Exercise, yoga, mindfulness, relaxation, paced breathing, cooling techniques and avoiding triggers are not recommended as treatments: when tested against control conditions, they did not reduce hot flashes. That does not make them useless. Exercise has broad benefits, and the National Institute on Aging’s practical advice, such as dressing in layers, keeping the bedroom cool and limiting alcohol, spicy food and caffeine, can make individual flashes easier to live with. Just do not expect them to make the flashes go away.

Supplements

Black cohosh is the most purchased botanical for menopause symptoms, but its active ingredients are unknown and trial results are inconsistent. The Menopause Society does not recommend supplements or herbal remedies, soy foods or extracts, or cannabinoids for hot flashes. If you take any supplement, tell your clinician, since several interact with prescription drugs.

When to see a clinician

Make an appointment if hot flashes:

• wake you regularly or leave you exhausted during the day
• come with heavy or prolonged bleeding, or any bleeding after your periods have stopped for a year
• are accompanied by unexplained weight loss, a persistently fast heartbeat, tremor or fever
• are affecting your mood, work or relationships

You do not have to wait until symptoms are severe. A clinician trained in menopause can walk through the options above in one visit. If your current provider is dismissive, here is how to find a menopause specialist, or search the directory.