What should you know about reason behind irregular period?

Irregular periods can happen when ovulation or hormone signals change, including with stress, weight change, polycystic ovary syndrome, perimenopause or some medicines. Pregnancy, breastfeeding and hormonal contraception can also alter bleeding. One unusual cycle is not enough to identify a cause, but a repeated change deserves a clinical review.

When ovulation does not occur regularly, periods may arrive late, skip or become unpredictable; this is called anovulation. Polycystic ovary syndrome can affect ovulation alongside acne, increased facial hair or difficulty conceiving. Perimenopause may bring changing cycle length as ovarian hormone production shifts. Premature ovarian insufficiency is another possible explanation when periods stop earlier than expected. These patterns overlap, so symptoms and testing matter more than one calendar entry.

Record the first day of each bleed, its duration, flow, pain, spotting, medicines and pregnancy possibility. Arrange an appointment if the pattern persists, periods stop, or you have troublesome acne, excess hair, hot flushes or fertility concerns. A clinician may discuss a pregnancy test, blood tests, examination or ultrasound. Treatment is chosen for the cause and your goals; options may include the [Combined Pill](/treatments/contraception-and-family-planning/combined-pill/) or [Metformin for PCOS](/treatments/medical-gynaecology/metformin-for-pcos/).

Seek urgent care for very heavy bleeding with weakness or dizziness, severe pelvic pain, fainting, or bleeding during a possible pregnancy. Contact a clinician sooner if periods stop unexpectedly or irregular bleeding follows menopause. See [Irregular Periods](/symptoms/irregular-periods/) for related guidance.

Ask what your cycle pattern suggests, whether pregnancy or thyroid-related problems need checking, and which tests could clarify ovulation. Discuss how any treatment affects contraception, bleeding, metabolic health and plans for pregnancy.