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Irregular periods
Category: Women's Health · All women's health symptoms
What it can feel like
Irregular periods means cycles that vary a lot in length, arrive unpredictably, or have changed pattern from your usual — cycles shorter than about three weeks or longer than about five, or gaps of months. Occasional irregularity is normal in the teens and in the years before the menopause; patterns in between deserve a system.
Possible causes
A symptom can have many causes, and most are not serious. The lists below group conditions this symptom can be associated with — common causes first. They are possibilities to discuss with a clinician, not a diagnosis.
Common causes
Irregular periods can be associated with stress, weight change, heavy exercise, polycystic ovary syndrome (the commonest cause, often with acne and extra hair growth), thyroid problems, and the perimenopause.
Other possible causes
Irregular periods can also be associated with raised prolactin hormone, premature ovarian insufficiency, uterine polyps or fibroids affecting bleeding pattern, and medicines including hormonal contraception and some psychiatric drugs.
Red flags — when to seek help promptly
- Periods that stop for more than three months in someone previously regular (and not pregnant)
- Irregular bleeding with dizziness, severe pelvic pain or fainting
- Irregular periods with milky nipple discharge or new coarse hair growth and voice change
- Bleeding after the menopause at any point — always assess
- Very heavy irregular bleeding causing anaemia symptoms
What a clinician may do
A clinician will map the cycle pattern (an app or diary record helps), ask about weight, exercise, hair, acne and medicines, and arrange a pregnancy test, blood tests for thyroid, prolactin and androgens, and a pelvic ultrasound where indicated.
Watch: related videos
Examination and clinical videos from the MedicalVideos.com library relevant to this symptom. Some clinical footage is graphic — that is the nature of a medical video library.
Related guides on MedicalVideos.com
Frequently asked questions
How irregular is irregular?
Cycles naturally vary by a few days. Clinicians take notice when cycle length varies by more than about a week to ten days month to month, when cycles regularly fall outside roughly 24–38 days in adults, or when periods vanish for over three months.
Why check my thyroid for a period problem?
The thyroid and reproductive hormones are wired together — both over- and under-activity disturb ovulation and cycle timing. It is one of the reversible causes, which is why it is in the first blood panel for irregular periods.
Related symptoms — Women's Health
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