Irregular periods in perimenopause: what's normal and what isn't
Irregular periods are the defining sign of perimenopause. Cycles often get shorter first, then start to vary by a week or more, and later skip for two months or longer. Bleeding can become heavier or lighter. These changes are normal — but very heavy bleeding, bleeding between periods or after sex, and any bleeding after 12 months without a period need a doctor.
How periods typically change
| Phase | What cycles do | What it means |
|---|---|---|
| Late reproductive | Slightly shorter cycles (e.g. 28 → 24–25 days) | Earlier ovulation, follicles depleting |
| Early perimenopause | Cycle lengths vary by 7+ days, persistently | STRAW+10 early transition |
| Late perimenopause | Gaps of 60+ days | STRAW+10 late transition |
| Menopause | 12 months with no period | Final period confirmed in hindsight |
Because ovulation becomes unpredictable, some cycles have high estrogen without the balancing progesterone — the lining builds up more, which is why some periods become heavy or long.
Normal vs. needs checking
Usually normal in perimenopause:
- cycles that are shorter, longer or unpredictable;
- an occasional heavier period;
- skipping a period or two, then periods returning;
- spotting just before a period.
See a doctor about:
- soaking a pad or tampon every 1–2 hours, passing large clots, or bleeding for more than 7 days — this can cause anaemia;
- bleeding between periods or after sex;
- periods closer together than every 21 days, persistently;
- any bleeding after 12 months without a period — always needs checking.
Heavy bleeding has treatments (hormonal IUDs, tranexamic acid, others), and checking iron levels is worthwhile if you feel exhausted.
Can I still get pregnant?
Yes. Irregular cycles still sometimes include ovulation. Contraception is usually advised until 12 months without periods if you are over 50, or 24 months if under 50.
Tracking periods when they are unpredictable
A regular period app tries to predict the next period from the average — which doesn't work when cycles swing between 21 and 60 days, and many apps call that an error. In perimenopause what matters is the pattern of variation: how much consecutive cycles differ and whether gaps reach 60 days, because that is what defines your stage. MenoShift records cycle lengths as they really are, shows your stage on the STRAW+10 scale, and lets you import periods logged in Apple Health by other apps.
MenoShift turns a 20-second daily check-in, your cycle and your Apple Watch nights into a plain explanation of the day — with the source. No account; nothing leaves your phone.
Download MenoShift on the App StoreFAQ
Why are my periods every two weeks in perimenopause?
Very short cycles can happen when ovulation comes early or when bleeding happens without ovulation. If it persists for several months, or bleeding is heavy, see a doctor to rule out other causes.
Is it normal to skip a period at 45?
Yes, skipped periods are common in later perimenopause. Take a pregnancy test if there's any chance of pregnancy.
Why are perimenopause periods so heavy?
Cycles without ovulation can leave estrogen unopposed by progesterone, so the womb lining thickens more and sheds more heavily.
My period came back after 8 months — is that normal?
Periods can return after long gaps in late perimenopause. The 12-month count restarts. Bleeding after a full 12 months, however, should always be checked.
Sources: STRAW+10 (Harlow et al., 2012); NICE guideline NG88 (Heavy menstrual bleeding) and NG23 (Menopause); Faculty of Sexual & Reproductive Healthcare, Contraception for women aged over 40 years.
Related
This guide is general information, not medical advice. If symptoms worry you — especially bleeding after 12 months without a period, very heavy bleeding, or chest pain — see a clinician.