Why am I so tired in perimenopause?

CommonMostly the nightTest first

Tired on waking as if the night did not count, or a wall at three, or flat all day. Most of it is the night arriving in the day, and the rest is two things a blood test finds.

Tonight, in three steps

Write down when you are most tired: on waking, mid-afternoon, or all day
Book the blood tests tomorrow: full blood count, ferritin, thyroid function
Protect the night before anything else, because the day follows it

Jump to what I would do first

38%

of women in the SWAN study reported difficulty sleeping, peaking in late perimenopause

Kravitz et al., Menopause, 2003

61%

less likely to be anaemic at the end of a trial were menstruating women given daily iron, across ten studies

Low et al., Cochrane, 2016

16 years

of follow-up in SWAN found symptoms cluster together across the transition rather than arriving one at a time

Harlow et al., Womens Midlife Health, 2017

The short answer

Fatigue in the transition is mostly the night arriving in the day, and it hides two things a blood test finds.

Yes, fatigue is a symptom of perimenopause, and it usually comes from the night: sleep that breaks at 3am, sleep that stays aroused even when it looks like eight hours, and flushes on top. It also hides behind low iron from heavier periods and an underactive thyroid, both of which a blood test finds and both of which are treatable.

Start with the night, because the day follows it. In the SWAN cohort, 38% of women reported difficulty sleeping, peaking in late perimenopause, and when sleep was followed through the transition, waking in the night was the most frequent complaint. That is the 3am wake, and it has its own page. Fewer hours and broken hours is the simplest reason a woman in this decade is tired, and it is the one most often waved away as stress.

Then the part that explains the tiredness that eight hours does not fix. When SWAN measured sleep with electrodes rather than questionnaires, women who moved into postmenopause showed increased fast-wave activity during non-REM sleep, which the researchers describe as physiological hyperarousal during sleep, and it held after controlling for hot flushes. The sleep looks like sleep on the clock and is doing less of the work. That is why you can be in bed nine hours and wake unrestored.

Then the two things fatigue hides behind, and this is the paragraph that matters most. Periods often get heavier in the transition, and an Australian clinical service says plainly that you might feel very tired or exhausted because of low iron if you have heavy periods. Iron deficiency is common, it is cheap to test, and the Cochrane review of daily iron in menstruating women found it reduces anaemia, improves exercise performance and reduces symptomatic fatigue. An underactive thyroid presents as tiredness, feeling cold, weight gain and low mood, which is also what the transition looks like, and it needs one blood test to separate.

Symptoms in this decade arrive together. Sixteen years of SWAN follow-up found they cluster rather than come one at a time, which is why fatigue so often travels with joint aches, low mood and brain fog, and why treating the sleep tends to move more than the sleep. The mistake is to treat each one as its own problem with its own supplement. The mechanism is shared, and so is most of the answer.

The usual causes

the 3am wakesleep that stays arousednight sweatslow iron from heavier periodsan underactive thyroidlow mood underneath

What you need to know

TLDR, if you are in a rush.

Fatigue is a symptom of perimenopause, and it is mostly the night. 38% of women in SWAN reported difficulty sleeping, and night waking was the most frequent complaint.

It is also why eight hours does not fix it: measured sleep in the transition shows physiological hyperarousal even when the clock looks fine.

Two things hide behind it, and both are a blood test: low iron from heavier periods, and an underactive thyroid. Ask for a full blood count, ferritin and thyroid function before buying anything.

Iron, where it is low, works. A Cochrane review of daily iron in menstruating women found it reduces anaemia and symptomatic fatigue.

See a GP this week if the fatigue is with weight loss, night sweats you would call drenching, breathlessness, a racing heart, or is so heavy you cannot function. Those are not the transition.

Before tonight

Four things to settle before you try anything.

Which tiredness

There are three shapes and they point different ways. Tired on waking, better by mid-morning, is the night. A collapse at three in the afternoon is blood sugar and the night together. Tired all day, every day, with no good hours, is the one that wants a blood test first.

The night, first

Everything on this page comes second to the 3am wake, because a day cannot outrun a broken night. If you are waking, that page is the one to run first. Magnesium, a protein dinner, a cooler room, no alcohol for a fortnight.

The blood tests

A full blood count, ferritin and thyroid function. All three are ordinary, all three are cheap, and between them they cover the two treatable things fatigue hides behind. Ask for the ferritin number, not just whether it is in range, because the bottom of the range is not the same as enough.

The photograph

Not a photograph this time, a log. Two weeks of one line a day: hours slept, times woken, energy out of ten at ten, two and six, and cycle day. A tiredness that tracks the cycle is hormonal. One that does not move is the one for the GP.

Searching moments

When women go looking for this.

I slept eight hours and woke exhausted

That is the measured version. In the transition, sleep shows raised arousal on the electrodes even when the hours are there. The night is not doing its full work. Fixing the wake and the temperature of the room does more than adding a ninth hour.

I hit a wall at three every afternoon

Usually the night and lunch together. A carbohydrate-heavy lunch on a short night lands as a collapse at three. Protein at lunch, and the walk after it, is the cheapest test of that.

My periods are heavier and I am wrung out

That is the pair to take to a GP. Heavier periods in the transition are common, and iron loss follows. Ask for ferritin specifically. If it is low, iron is one of the few supplements on this site with a Cochrane review behind it.

I am cold, tired and gaining weight

Ask for three blood tests

A full blood count, ferritin and thyroid function. These cover the two treatable things fatigue hides behind: iron loss from heavier periods, and an underactive thyroid. Ask for the ferritin figure itself. If it is low, daily iron has a Cochrane review behind it for reducing anaemia and symptomatic fatigue. If the thyroid is slow, that is a treatment, not a supplement.

Results in a week, and they set the direction

Log two weeks of sleep and energy

One line a day: hours slept, the times you woke, energy out of ten at ten, two and six, and the cycle day. A fatigue that clusters before a period is hormonal. One that follows a broken night is the night. One that never moves is the one for the GP conversation.

Fourteen days, then read it

Fix the night before the day

If you are waking at 3am, run that page: magnesium glycinate in the evening, a protein dinner, a cooler and darker room, no alcohol for a fortnight. A day cannot be repaired from the day end. In SWAN the night waking was the most frequent sleep complaint of the transition, and it is upstream of almost everything else here.

Three to four weeks before you judge it

Protein at lunch, and a walk after it

The three o'clock collapse is a short night meeting a carbohydrate lunch. Protein and fat at lunch, caffeine before ten with food and not after, and twenty minutes of walking in daylight after eating. This is the cheapest and fastest change on the page.

Afternoons steady within a week

Move, at the right dose

Walking in morning light and two short strength sessions a week. Not hard training on broken nights, which raises cortisol and deepens the hole. Strength work in this decade has evidence for mood, and mood and fatigue travel together.

Energy improves before fitness does, usually inside a month

This month

The habits that change the baseline.

The moves above find the cause. These keep the baseline up.

Same wake time, including weekends

A fixed wake time does more for a broken night than an early bedtime, because it anchors the rhythm that the transition is loosening.

Daylight before screens

Ten minutes outside in the first hour sets the cortisol rhythm for the day. It is free, and it is the single most reliable lever for morning energy.

Caffeine before ten, with food

Not none. Just early, and not on an empty stomach, so it lifts the morning without fragmenting the night.

Protein at every meal

It steadies the blood sugar that a short night makes volatile. The afternoon collapse is usually lunch, not laziness.

Ferritin rechecked after three months on iron

If iron was started, it needs a recheck, because taking it forever is not the plan and neither is stopping it early.

A fortnight without alcohol, then decide

Alcohol fragments the second half of the night. Most women who try a fortnight without it do not need to be told the result.

Research notes

Source-backed signals for this page.

Each line is a specific figure or finding, with where it came from. Nothing on this page is guessed.

In the SWAN cohort, 38% of women reported difficulty sleeping, with the highest rates in late perimenopause.

Kravitz et al., Menopause, 2003

Followed through the transition, sleep disturbance rose and waking during the night was the most frequently reported complaint.

Kravitz et al., Sleep, 2008

Measured with polysomnography, women who transitioned to postmenopause showed increased beta EEG power in non-REM sleep, which the authors describe as physiological hyperarousal during sleep, independent of self-reported hot flushes.

Matthews et al., Sleep, 2021

An Australian clinical service says that during perimenopause you might feel very tired or exhausted because of low iron levels if you have heavy periods.

Jean Hailes, Menopause

A Cochrane review of 67 trials in 8,506 menstruating women found daily iron made women 61% less likely to be anaemic at the end of a trial, improved exercise performance and reduced symptomatic fatigue.

Low et al., Cochrane, 2016

Over 16 years and eight visits, SWAN found symptoms cluster across the transition rather than arriving singly, with physical, psychological and menopausal symptoms travelling together.

Harlow et al., Womens Midlife Health, 2017

An underactive thyroid presents with tiredness, feeling cold, weight gain and low mood, which overlaps the transition and is separated by a blood test.

healthdirect, Hypothyroidism

The studies

The research behind the advice.

Not testimonials. The studies that give the moves above their standing, with what was tested and what was found.

01 · Sleep 44(11), longitudinal polysomnography, 2021

Why eight hours stops working

What was tested: Whether the menopausal transition changes the physiology of sleep, not just the report of it.
How: SWAN participants had in-home polysomnography at two points several years apart, grouped by whether they stayed pre- or early perimenopausal or moved to postmenopause, with hot flushes controlled for.
What was found: Women who transitioned showed increased beta EEG power during non-REM sleep, a marker of arousal, with no change in total sleep time or time awake after sleep onset. The finding held after adjusting for self-reported flushes.
What it means for you: The hours can be there and the sleep can still be shallower than it was. That is the tiredness that a lie-in does not touch, and it is why the night's quality matters more than its length.

View source

02 · Cochrane Database of Systematic Reviews, 67 trials, 2016

The one supplement with a review behind it

What was tested: Whether daily iron improves anaemia, iron status and health in menstruating women.
How: A systematic review of 67 randomised trials recruiting 8,506 women, with anaemia at the end of intervention as the primary outcome and exercise performance and fatigue among the secondary ones.
What was found: Women receiving iron were 61% less likely to be anaemic, had higher haemoglobin, had reduced risk of iron deficiency, and the review reports improved exercise performance and reduced symptomatic fatigue.
What it means for you: Where ferritin is low, iron is not a wellness purchase, it is a treatment with evidence. Where ferritin is fine, it does nothing for tiredness, which is why the test comes first.

View source

03 · Womens Midlife Health 3, latent transition analysis, 2017

Symptoms arrive in company

What was tested: Whether midlife symptoms cluster, and whether the clusters shift across the stages of the transition.
How: 3,289 SWAN participants reported on 58 symptoms at baseline and seven follow-ups over 16 years, analysed by stage from premenopause to postmenopause.
What was found: Symptoms clustered into recognisable groups rather than appearing singly, and the clusters moved with reproductive stage.
What it means for you: Fatigue rarely comes alone in this decade, which is both why it is so easily dismissed and why fixing the night tends to move the mood and the aches with it.

View source

Comparison

Is it the transition, or something a blood test finds?

Three causes of tiredness that look alike from the inside, and the questions that separate them.

	The transition	Low iron	Thyroid
What it feels like	Tired on waking, worse after a broken night, better on a good one. Often with brain fog and low mood.	Wrung out, breathless on stairs, pale, restless legs at night, hair shedding.	Tired all day with no good hours, cold, gaining weight, constipated, low.
What it travels with	The 3am wake, warm nights, cycle changes, anxiety.	Heavier or longer periods, or a diet low in red meat.	Feeling cold when others do not, dry skin, thinning hair, a slower pulse.
The pattern	Follows the night and the cycle. Good days exist.	Steady and worsening with each heavy period.	Steady, and does not lift with sleep.
What separates it	A two-week sleep and energy log.	Ferritin, not just haemoglobin.	Thyroid function, one test.
What answers it	The night: the 3am protocol, the room, alcohol out, protein and daylight.	Iron, with a Cochrane review behind it, and rechecked at three months.	Treatment from a GP. No supplement replaces it.

Fit check

Who this page is for, and when to see a GP instead.

This will help if

you are between 38 and 55 and more tired than your life explains
the tiredness is worse after broken nights and better after good ones
your periods have changed, particularly if they are heavier
it arrived alongside other things: warm nights, brain fog, low mood, aching joints

See a GP instead when

the fatigue comes with weight loss you did not intend, fevers, or night sweats you would call drenching
you are breathless on ordinary effort, or your heart races or thumps at rest
it is so heavy you cannot work or run the household, or it has run more than three months without a good week
it comes with feeling cold, weight gain and constipation: ask for thyroid function
your periods are heavy, you are pale or breathless: ask for a full blood count and ferritin
mood is heavy, or you have stopped wanting things you used to want, which is a conversation this week rather than a supplement

By situation

The same rules, applied to your case.

Fatigue with the 3am wakeAsleep by ten, awake at three, wrecked by two.

The most common version and the most fixable. The wake is upstream of the day, and in SWAN it was the most frequent sleep complaint of the transition. Run the 3am page's first moves and give them three to four weeks.

Then

If the wake settles and the fatigue does not, that is when the blood tests earn their place.

Fatigue with heavy periodsThe month gets worse as the period approaches, and the week after is the floor.

That pattern is iron, until a test says otherwise. Heavier periods in the transition are common, and an Australian service names the tiredness that follows them plainly. Ask for ferritin specifically.

Then

Where ferritin is low, daily iron has a Cochrane review behind it for reducing anaemia and symptomatic fatigue. Recheck at three months.

Fatigue with joint achesTired and sore, and neither one explains the other.

In SWAN's sixteen-year follow-up, symptoms clustered rather than arriving one at a time, and aching joints and fatigue are a common pair in the transition. A broken night lowers the pain threshold, and pain breaks the night.

Then

There is a page for the joints. Run the night first, because it moves both.

Fatigue before a periodTen days of it, then a lift.

That is the hormonal shape: progesterone falling in the second half of the cycle takes sleep quality and mood with it, and both take energy. A log that shows the cluster is strong evidence for a GP.

Then

Track it against the cycle for two months. A pattern on paper changes what a prescriber suggests.

Fatigue on menopausal hormone therapy (MHT, or HRT)Prescribed for the flushes, and still flat.

Hormone therapy addresses the flushes and often the sleep. It does not address low iron or a slow thyroid, and it does not fix a night broken by alcohol or caffeine. The blood tests and the log still apply.

Then

Take a two-week log to the next review. Dose, route and timing are all adjustable.

The seven-day plan

One change a day, in the order they matter.

A week of finding the cause, then a fortnight of protecting the night. The blood tests are day one because their result decides the rest.

Day one

Ring for the blood tests: full blood count, ferritin, thyroid function. Start the log tonight: hours, wakes, energy at ten, two and six, cycle day.

Day two

Caffeine before ten with food, none after. Protein and fat at lunch. Twenty minutes walking in daylight after eating.

Day three

Bedroom cooler than feels normal, phone out of it, the same wake time set for every day this fortnight.

Day four

No alcohol from tonight for fourteen days. This is the test most women do not need to be told the result of.

Day five

If you wake at 3am, start that page's first moves tonight: magnesium glycinate in the evening, a protein dinner.

Day six

Ten minutes outside in the first hour of the day. Two short strength sessions a week, not a hard one.

Day seven

Read the log and the blood results together. Low ferritin or a slow thyroid means a GP conversation this week. Neither means a fortnight more of the night, then judge.

Questions

What women ask before they try this.

Yes, and a common one. It mostly comes from the night: in the SWAN study 38% of women reported difficulty sleeping, night waking was the most frequent complaint, and measured sleep in the transition shows raised arousal even when the hours look fine. It also hides behind two things a blood test finds, low iron from heavier periods and an underactive thyroid, which is why those tests come before anything else.

Three reasons, usually together. Progesterone falls first and its calming metabolite with it, so sleep breaks at 3am. Sleep that looks intact on the clock shows physiological hyperarousal on the electrodes, so eight hours does less work. And flushes at night wake you. Underneath, heavier periods drain iron, and the whole cluster lowers mood, which takes energy with it.

Tired on waking as if the night did not count, or a wall at three in the afternoon, or flat all day with no good hours. The first two follow the night and the cycle and have good days. The third is the one that wants a blood test first, because tired all day every day is also what low iron and an underactive thyroid look like.

It can feel extreme, particularly when a broken night, night sweats and heavier periods stack. But extreme fatigue that comes with weight loss, drenching sweats, breathlessness, a racing heart, or that stops you functioning, should not be put down to the transition without a GP visit and blood tests. The ordinary version has good days in it.

Because the luteal phase, the second half of the cycle, is where progesterone falls fastest, and in the transition it falls from a more erratic baseline. Sleep quality and mood both drop in that window and energy follows. A log that shows fatigue clustering in the seven to ten days before bleeding and lifting afterwards is the hormonal pattern, and it is strong evidence to bring a GP.

In order: the blood tests, because low iron and a slow thyroid are treatable and nothing else touches them. Then the night: the 3am protocol, a cooler room, alcohol out for a fortnight. Then the day: caffeine before ten, protein at lunch, a walk in daylight, two short strength sessions a week. Of the natural remedies, magnesium glycinate for the night is the one with a reason behind it. Relief usually comes from those foundations rather than from anything sold for energy.

One does, in one situation. Daily iron, where ferritin is low, has a Cochrane review behind it: less anaemia, better exercise performance, less symptomatic fatigue. Where ferritin is fine it does nothing. Magnesium glycinate helps the night, which helps the day. Nothing sold as an energy formula has evidence for this, and none of it addresses a thyroid.

As long as the cause does, and it gets worse when the cause is untreated: iron keeps falling with each heavy period, and a broken night compounds. Where it is the night, three to four weeks of protecting sleep usually moves it. Where it is iron, three months of treatment and a recheck. Where it is thyroid, it lifts with treatment. Where it is the transition itself, it tends to ease as the cycle settles, but that can be years, which is why the treatable causes are worth finding first.

It could, and the test is easy. An underactive thyroid presents as tired, cold, gaining weight, constipated and low, which is exactly the picture women attribute to hormones. One blood test separates them, it belongs in the first fortnight rather than after a year of trying things, and if it is the thyroid, the treatment works.

This week if it comes with weight loss, fevers, drenching night sweats, breathlessness, a racing heart, or if you cannot function. Soon if it has run three months without a good week, if your periods are heavy, or if you are cold and gaining weight. Ask for a full blood count, ferritin and thyroid function. Bring a two-week sleep and energy log.

Keep reading

Related symptoms, and the articles that go with this one.

The 3am wakeWhy do I wake at 3am in perimenopause?You fall asleep fine, then wake at 3am, wide awake, heart going. It is one of the earliest and most reliable signs of the transition, and it has a mechanism.Brain fogWhy do I have brain fog in perimenopause?The word goes missing mid-sentence. You walk into a room and forget why. It is one of the most frightening symptoms, because of what women fear it means, and it is a documented part of the transition.New anxietyWhy am I anxious for the first time in perimenopause?A new edginess. Anxiety in a way that is unfamiliar, often worst in the days before a period. For many women it is the symptom that is hardest to attribute to the transition.Aching jointsWhy do my joints ache in perimenopause?Stiff on waking, slow out of a chair, hands and knees and hips. The most commonly reported symptom of the transition in Australian data, and mostly not the joint wearing out.Read nextThe 3am wake up, explainedIf you fall asleep fine and wake at 3am, wide awake, heart racing, mind cycling, you are not broken. There is a mechanism, and it has a name.Also readThe hormone panel worth asking forThe tests worth requesting, the hormone panel your doctor is right to decline after 45, and how to make the appointment count.

References

Sources used on this page.

Every figure and finding above traces to one of these.

Sleep difficulty in women at midlife: a community survey of sleep and the menopausal transition

Kravitz et al., Menopause 10(1), the SWAN study, 2003.

The 38% figure for sleep difficulty and its peak in late perimenopause.

Sleep disturbance during the menopausal transition in a multi-ethnic community sample of women

Kravitz et al., Sleep 31(7), the SWAN study, 2008.

Sleep disturbance followed through the transition, with night waking the most frequent complaint.

Influence of the menopausal transition on polysomnographic sleep characteristics: a longitudinal analysis

Matthews et al., Sleep 44(11), the SWAN Sleep Study, 2021.

Increased beta EEG power in non-REM sleep among women who transitioned to postmenopause, described as physiological hyperarousal during sleep, independent of self-reported hot flushes, with no change in sleep duration.

Daily iron supplementation for improving anaemia, iron status and health in menstruating women

Low et al., Cochrane Database of Systematic Reviews 4, 2016.

The 67 trials and 8,506 women, the 61% reduction in anaemia (risk ratio 0.39), improved exercise performance, and reduced symptomatic fatigue.

It is not just menopause: symptom clustering in the Study of Women's Health Across the Nation

Harlow et al., Womens Midlife Health 3, 2017.

Symptoms clustering across the transition over 16 years and eight visits in 3,289 women, rather than arriving singly.

Menopause

Jean Hailes for Women's Health, accessed September 2026.

Feeling very tired or exhausted because of low iron with heavy periods, and poor sleep, aches and mood changes as the other major symptoms.

Hypothyroidism (underactive thyroid)

healthdirect, accessed September 2026.

The symptom picture of an underactive thyroid: tiredness, feeling cold, weight gain, low mood.

Written by Davina Hearne, 11 September 2026.

Davina Hearne qualified in 2012 at Wellpark College of Natural Therapies in New Zealand, with three NZQA Level 6 diplomas taken together over three years: Naturopathy, Herbal Medicine and Nutrition.

Davina Hearne is a New Zealand qualified naturopath, herbalist and nutritionist. She is not a medical doctor. This is health education from a qualified non-physician practitioner. It is not medical advice and does not establish a practitioner relationship.

Start tonight

Book the three blood tests, then protect the night.

Most of this decade's tiredness is the night arriving in the day, and most of the rest is iron or thyroid, which a blood test finds and treatment fixes. Ring for the tests tomorrow, start the log tonight, and run the 3am page if you are waking. Give the night three to four weeks. Nothing sold for energy does what those three things do.

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