Irregular period on the pill: what to know

Spotting or a change in withdrawal bleeding is common when starting or changing a pill, and it may settle as your body adjusts. Taking tablets late, missing tablets, vomiting, or having diarrhoea can reduce contraceptive protection depending on the situation. Some medicines can also affect how the pill works. Bleeding after sex, new pelvic pain, unusual discharge, or pregnancy symptoms deserve separate attention. Conditions such as polycystic ovary syndrome, anovulation, or perimenopause can also affect bleeding, although the pill can mask the underlying pattern.

Record the days you take active tablets, any missed or late doses, spotting, pain, and other medicines. Follow the instructions for your specific pill rather than doubling doses without checking. If pregnancy is possible, take a pregnancy test and ask a pharmacist or clinician how to maintain protection. A clinician can review whether a different pill, another contraceptive method, or assessment for a condition such as PCOS is appropriate. Read more about the [Combined Pill](/treatments/contraception-and-family-planning/combined-pill/) and [Irregular Periods](/symptoms/irregular-periods/).

Arrange medical advice for bleeding that keeps returning, occurs after sex, or comes with pelvic pain, fever, dizziness, or marked tiredness. Seek urgent help for very heavy bleeding with faintness, severe or one-sided abdominal pain, or bleeding when pregnancy is possible. Do not stop a prescribed pill without discussing a replacement plan if pregnancy prevention is important.

Could a missed dose, interaction, or pregnancy explain this pattern? Does my pill need changing? Should I have an examination or tests for PCOS, thyroid problems, or another cause? What should I do if the bleeding becomes heavy?