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Irregular periods in perimenopause: what's normal and what isn't
Erratic periods are usually the first sign of perimenopause. When the length of consecutive cycles keeps differing by 7 days or more, you're in the early transition. A gap of 60 days or more without a period marks the late transition, which STRAW+10 estimates lasts 1 to 3 years on average. Some irregularity is expected, but bleeding between periods, after sex, or lasting longer than 7 days needs a doctor.
Cycles that shift by 7+ days mark early perimenopause; gaps of 60+ days mark the late stage. What's normal, which bleeding needs a doctor, and how to track it.
Perimenopause periods: what women expect vs what happens
What people often expect
“Periods just get lighter and further apart until they stop”
What the evidence shows
The NHS lists periods that come more often or less often, and bleeding that gets heavier or lighter, among the first signs of perimenopause, not only lighter and further apart. STRAW+10 describes cycles getting shorter in late reproductive life before gaps widen, so the pattern can feel chaotic long before periods stop. Heavier, longer and closer-together periods are all part of the normal range.
Why periods become irregular in perimenopause
The ovaries run low on eggs and the cycle loses its rhythm
Perimenopause follows the gradual loss of eggs from the ovaries and falling ovarian hormones. The brain-ovary loop that once ran steadily turns erratic, with wide hormonal fluctuations and irregular bleeding. Some cycles still release an egg and some don't, which is why cycle length and flow can change from one month to the next without a clear trend. A review of the menopause transition describes it as a disruptive process that can last for over a decade.
Shorter cycles come first, then skipped periods
STRAW+10, the standard staging system for reproductive aging, maps the typical sequence. In late reproductive life, cycles often get subtly shorter. In the early transition, cycle length becomes variable, defined as a difference of 7 days or more between consecutive cycles that comes back within 10 cycles. In the late transition, you start skipping periods, with gaps of 60 days or more, and hormone levels swing to extremes.
Low progesterone makes periods late, long or heavy
When ovulation is absent or weak, there is little progesterone to steady the uterine lining. Estrogen keeps building the lining up, and it sheds unpredictably: early, late, light, or heavy and long. Researchers who study perimenopause point out that estrogen levels often run higher than before and soar erratically, while progesterone falls. That combination explains the long, heavy periods many women get in their 40s, and why about a quarter have heavy menstrual bleeding.
Hormone changes start before your periods look different
In a study that followed women aged 35 to 47 for 5 years, even subtle shifts in cycle length already tracked meaningful changes in inhibin B and FSH, the hormones that reflect ovarian reserve, while estradiol levels didn't differ. So if your cycle has started drifting by a few days, the transition may already be underway, even if you have no hot flashes yet.
Fibroids and polyps add to irregular bleeding in your 40s
Not all irregular bleeding in perimenopause is hormonal. Benign growths such as endometrial polyps and fibroids become more common with age and lead to more abnormal bleeding around this time. They typically cause bleeding between periods or periods that become much heavier. A transvaginal ultrasound is the usual first test, and treatment depends on what it shows. If bleeding between periods keeps happening, get it checked rather than assuming it is hormonal.
Perimenopause cycle changes by the numbers
21–35 days
7+ days
60+ days
45–55
Almost every woman's cycle changes before menopause. What varies is how: some go straight to skipped periods, others have months of short, heavy or long cycles first.
Irregular periods that aren't perimenopause
Perimenopause is the most likely reason for erratic periods in your 40s, but not the only one. Rule these out, starting with pregnancy.
Pregnancy
Check →A missed or late period, sore breasts, nausea. You can still get pregnant in perimenopause, because ovulation becomes unpredictable, not absent.
Test: Pregnancy test
Thyroid problems
Check →Irregular periods with tiredness, weight change, or feeling cold or hot all the time.
Test: TSH blood test
PCOS (PMOS)
Irregular periods for years, not just recently, with extra facial or body hair, acne and weight gain.
Test: Doctor's assessment
Hormonal contraception
Mini-pill, injection or hormonal IUD. Bleeding reflects the method, not your natural cycle.
Test: None, it's expected
Polyps or fibroids
Check →Bleeding between periods, or periods getting much heavier or longer, sometimes with pelvic pressure.
Test: Transvaginal ultrasound
Weight change, stress or heavy exercise
A big change in weight, a stressful stretch or a jump in training shortly before the change.
Test: Doctor's assessment if it continues
What helps with irregular periods in perimenopause
Track every cycle
First stepUse an app or a diary and log the first day of each period, how heavy it is and how long it lasts. Day 1 is the first day of bleeding. STRAW+10 reads your stage from cycle-length patterns, and a record makes it much easier for your doctor to see whether bleeding fits perimenopause or needs tests. It also shows you when you've reached a 60-day gap.
Related guide →Hormonal treatment for irregular perimenopause bleeding
Strong evidenceOnce pregnancy, thyroid problems and structural causes are ruled out, oral progestogens, the combined pill or a levonorgestrel intrauterine system (hormonal IUD) can regulate bleeding from cycles without ovulation when it's interfering with daily life. If bleeding is irregular but light and not bothering you, watching and waiting is also a reasonable choice.
Related guide →Treat heavy periods
Strong evidenceHeavy bleeding that causes anemia needs prompt treatment. Tranexamic acid, anti-inflammatory painkillers such as ibuprofen, progestogens and the hormonal IUD all reduce blood loss. NICE asks for a full blood count in every woman with heavy periods and says treatment should aim to improve quality of life, not just reduce bleeding.
Related guide →Contraception until menopause is confirmed
If this is the causeIrregular periods don't mean you can't get pregnant. Keep using contraception until you've gone 12 months without a period. Some methods, such as the hormonal IUD, treat heavy or erratic bleeding and prevent pregnancy at the same time. Your doctor can help you choose a method that suits your bleeding pattern and health.
Related guide →
Period changes that need a doctor
Urgent: Any bleeding 12 months or more after your last period
Always needs checking, even if it's a small amount or happened once. You should not have to wait more than 2 weeks to see a specialist.
More →Bleeding between periods or after sex
See a doctor. Polyps, infection and, rarely, precancerous changes need ruling out.
Periods lasting longer than 7 days, or much heavier than before
See a doctor. The NHS advises checking if you're bleeding more, not less, than before, and heavy bleeding can cause anemia.
Irregular periods with other symptoms
Weight gain, tiredness, facial hair growth, or dry or oily skin alongside irregular periods: see a doctor to check for thyroid problems or PCOS.
Irregular periods in perimenopause: FAQ
Is it normal to have irregular periods at 45?
Yes. Irregular periods are common as you approach menopause, which usually happens between 45 and 55. In the early transition, cycles vary by 7 days or more; later, you start skipping periods. Still see a doctor if you bleed between periods, after sex, or if a period lasts more than 7 days.
Can I get pregnant if my periods are irregular in perimenopause?
Yes. Ovulation becomes unpredictable, not absent, and a late period can still be a pregnancy. Keep using contraception until you've had 12 months without a period, and take a pregnancy test if a period is late and there's any chance.
Related →How long do irregular periods last before menopause?
It varies. The late transition, when gaps reach 60 days or more, lasts 1 to 3 years on average. The early transition before it varies a lot between women. The NHS says menopause symptoms overall usually last 7 to 9 years, sometimes longer.
What counts as the early perimenopause cycle change?
A persistent difference of 7 days or more between the lengths of consecutive cycles, for example 26 days followed by 34 days, that happens again within 10 cycles. That is the STRAW+10 definition of the early menopausal transition.
Is a skipped or late period normal in perimenopause?
Yes. Skipped and late periods are typical as ovulation becomes irregular, and a gap of 60 days or more marks the late transition. Take a pregnancy test if there's any chance, because you can still conceive.
Why are my periods getting shorter and closer together in perimenopause?
Shorter cycles are often the first change. STRAW+10 describes cycles getting subtly shorter in late reproductive life, as the ovaries respond faster to rising FSH. A cycle shorter than 21 days counts as irregular. Frequent periods can also be heavier, so check for tiredness and breathlessness that could mean low iron.
Why are my periods longer in perimenopause?
Without regular ovulation, there's too little progesterone to steady the uterine lining, so it builds up and sheds unevenly, which can mean long, heavy periods. Fibroids and polyps, which become more common with age, can do the same. A period lasting more than 7 days is worth a doctor's visit.
Can perimenopause cause a period to be late by weeks?
Yes. In the late transition, periods can be 60 days or more apart. A late period can also be pregnancy, so test if there's any chance. If you're over 45, you don't need blood tests to confirm perimenopause: NICE advises diagnosing it from symptoms and cycle changes.
Do I need a blood test for irregular periods in perimenopause?
Usually not if you are 45 or over. NICE advises diagnosing perimenopause from symptoms and cycle changes without blood tests in that age group, because hormone levels swing too much to give a clear answer. Your doctor may still test for pregnancy, thyroid problems or anemia if your symptoms suggest them, and a hormone test can help if you are between 40 and 45.
Sources
- Harlow SD, Gass M, Hall JE, et al. Executive summary of the Stages of Reproductive Aging Workshop + 10. J Clin Endocrinol Metab. 2012;97(4):1159-1168.
- NHS. Irregular periods.
- NHS. Symptoms of menopause and perimenopause.
- Santoro N, Roeca C, Peters BA, et al. The Menopause Transition: Signs, Symptoms, and Management Options. J Clin Endocrinol Metab. 2021;106(1):1-15.
- Prior JC. Progesterone for Symptomatic Perimenopause Treatment - Progesterone politics, physiology and potential for perimenopause. Facts Views Vis Obgyn. 2011;3(2):109-20.
- Gracia CR, Sammel MD, Freeman EW, et al. Defining menopause status: creation of a new definition to identify the early changes of the menopausal transition. Menopause. 2005;12(2):128-35.
- Dreisler E, Frandsen CS, Ulrich L. Perimenopausal abnormal uterine bleeding. Maturitas. 2024;184:107944.
- NICE. Heavy menstrual bleeding: assessment and management (NG88).
- NICE. Menopause: identification and management (NG23). Updated 2024.
- NHS. Postmenopausal bleeding.
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