Hot Flushes, Chills and Night Sweats: Why Menopause Changes Your Body Temperature

Hot flushes are the symptom most of us associate with menopause, and up to 80 percent of women experience them.¹ But body temperature can swing both ways, and for many women this phase is just as much about sudden chills, damp sheets and broken nights. Here is what happens in the body, how long it tends to last, and what helps.

Why do hot flushes happen in menopause?

Body temperature is controlled by the hypothalamus, a small area of the brain that works as the body's thermostat. Normally it keeps your temperature within a narrow but comfortable range. Only when you get too warm do you start to sweat, and only when you get too cold do you start to shiver.²

Oestrogen helps keep a particular group of nerve cells in the hypothalamus in check. These cells regulate both the reproductive hormones and body temperature, and one of the signals that drives them is a messenger called neurokinin B. As oestrogen falls during menopause, that brake is released. The cells become overactive and send the thermostat false signals that the body is overheating.³ The role of neurokinin B has been confirmed in studies where women who had not yet reached menopause were given it intravenously, and promptly had classic hot flushes.⁴

At the same time, the comfortable range narrows. A tiny change in core temperature, or just the signal of one, is then enough for the body to switch its cooling on full. Blood vessels in the skin widen and the sweat glands start working to get rid of heat that isn't really there.²

What does a hot flush feel like?

A hot flush usually starts as a sudden, intense heat in the face, neck and upper chest that then spreads through the body. The skin reddens and many women sweat heavily. The flush itself typically lasts one to five minutes, but the aftermath, such as palpitations, anxiety or irritability, can linger longer.¹

How often they come varies enormously from woman to woman. Some have the occasional flush and find it manageable, others have several an hour. Flushes tend to build during late perimenopause and peak around a year after the final period, before easing off over several years.⁵

Why do you feel cold in menopause?

Cold flushes, sometimes called menopausal chills, get far less attention than hot flushes but are common. They arrive as a sudden, bone-deep cold, often with shivering and goosebumps, however warm the room is.⁶

Most often a cold flush follows straight after a hot one. Once the body has sweated and cooled, its temperature dips slightly, and because the comfortable range is now so narrow, the thermostat reads this normal cooling as a sign the body is getting too cold. Blood vessels tighten and the muscles start to shiver to generate heat.⁶ Chills can also come on their own, for example with stress, a sudden rush of adrenaline, or when oestrogen levels swing sharply from day to day in perimenopause.⁶

Because chills and feeling cold can have other causes too, it is worth checking your thyroid and iron levels (ferritin) and ruling out an infection if the symptoms are new or unusually strong.⁷ To make chills easier to live with, it can help to eat regularly so your blood sugar stays steady, cut back on coffee and alcohol, and wear clothes that wick moisture away, so the sweat from a hot flush doesn't chill you further.⁸

Why do you wake at 3 a.m.? Night sweats and sleep

When hot flushes happen at night they are called night sweats, and in many ways they are the hardest to live with. Body temperature naturally drops a little in the evening, which is part of what helps us fall and stay asleep. In menopause, that very drop, combined with the narrower comfort range, can set off a flush.⁹

The sudden rise in temperature wakes the brain, often with a racing pulse and a sense of unease, and getting back to sleep can be hard. That is why so many women in menopause recognise waking in the middle of the night, often around three.⁹ When sleep is broken night after night, both deep sleep and REM sleep suffer, and this is one of the main reasons behind the brain fog, irritability and low mood many women feel in these years.¹

How long do hot flushes last?

For a long time, hot flushes were thought to pass within six months or a couple of years. The American SWAN study, which has followed more than 3,300 women through menopause for around 25 years, has changed that picture. Half of the women had frequent hot flushes for more than 7.4 years. For women whose flushes began early, while they still had periods, the median was almost 12 years (11.8).¹⁰

The researchers also identified four distinct patterns in how hot flushes come and go:¹¹

It also means that hot flushes several years after your last period are entirely normal. You can read more about the phases of the transition in our guide to menopause.

What happens in surgical menopause?

If both ovaries are removed, for example because of endometriosis, cancer or an inherited risk such as a BRCA mutation, menopause arrives overnight. Oestrogen and progesterone production stops immediately, and the body's total testosterone production halves. Hot flushes can begin within days of the operation.¹²

Unlike natural menopause, where symptoms eventually ease for most women, they tend to stay high without treatment. If the operation happens before 45, the risk of osteoporosis, heart disease and cognitive decline also rises, which is why oestrogen therapy is generally recommended until around 51, unless there is a medical reason not to.¹² If you are facing this operation, it is worth raising with your gynaecologist in good time.

Can hot flushes say something about your heart?

Hot flushes were long seen purely as a quality-of-life issue. Research now increasingly treats them as an early signal of how your blood vessels are doing.¹³ In studies, women with frequent hot flushes show poorer function in the inner lining of their blood vessels, independent of age, weight and smoking.¹³ In SWAN, women whose frequent hot flushes persisted over time had a 50 to 77 percent higher risk of later cardiovascular disease,¹⁴ and in pooled data from more than 23,000 women it was above all severe hot flushes that were linked to higher risk.¹⁵

An association says nothing certain about what will happen to any one person. But if you have had severe hot flushes for a long time, it is a good reason to ask your GP to check your blood pressure, cholesterol and blood sugar.¹³

What helps with hot flushes?

What suits you depends on how bothersome the flushes are, your age and your own health history. For many women, a few changes in everyday life go a long way.

A cool bedroom, layers and other everyday tips

Many women find that small changes make hot flushes easier to manage. Dress in layers that are easy to take on and off, ideally in natural fabrics that breathe, and choose a lighter duvet without synthetic fibres. Keep your home, and especially your bedroom, a little cooler. Regular exercise that really makes you sweat can help your body handle sweating better, and cutting back on stress, coffee, alcohol and sugar, and stopping smoking, can reduce how often and how strongly hot flushes come.

If hot flushes are affecting your sleep or your daily life a lot, it is also worth seeking help rather than gritting your teeth.

Hormone therapy

Menopausal hormone therapy (MHT, often called HRT) remains the most effective medical treatment for hot flushes. It replaces the oestrogen your body no longer makes, which puts the brake back on those overactive nerve cells.¹⁶ For women under 60, or within 10 years of their last period, it is usually the first choice unless there is a reason against it, such as previous hormone-sensitive breast or womb cancer, a heart attack, a stroke or an inherited high risk of blood clots.¹⁶

CBT and hypnosis

Two treatments without medication have strong enough evidence to be recommended by The Menopause Society.¹⁶ CBT tailored to menopause does not necessarily reduce the number of hot flushes, but it makes them far less disruptive to daily life and improves sleep.¹⁷ In one study, hypnosis reduced self-reported hot flush scores by 80 percent.¹⁸

Supplements in menopause

HORMONES & ME is formulated for women in perimenopause and menopause, as daily support for the body through this phase. Among its ingredients are vitamin B6, which contributes to the regulation of hormonal activity and to the reduction of tiredness and fatigue, and magnesium, which also contributes to the reduction of tiredness and fatigue. When sweats break up your nights, it is often the tiredness the next day that you notice most.

HORMONES & ME is not recommended during pregnancy or breastfeeding, or for anyone under 18. If you have a thyroid disorder, liver or kidney disease, or take medication, speak to your doctor before starting. Supplements complement a varied diet and a healthy lifestyle, and can never replace them.