What should you know about random breakthrough bleeding on pill?

The pill changes the hormone pattern that controls the uterine lining. Spotting may occur during the first months of a new pill, after missed or late tablets, with vomiting or diarrhoea, or when another medicine affects how reliably the pill is absorbed. Continuous or extended use can also bring bleeding outside an expected break.

Breakthrough bleeding does not by itself show that the pill has failed, but missed doses can reduce contraceptive protection. Chlamydia can also present with abnormal bleeding, and an endometrial polyp is another possible cause. These possibilities require assessment rather than guessing from the bleeding.

Keep taking the pill according to its instructions unless a clinician tells you otherwise. Check whether any tablets were late or missed, and follow the product guidance for missed pills. Consider whether vomiting, diarrhoea or a new medicine occurred. Use additional contraception when the instructions advise it, and arrange a review if bleeding continues, returns after settling, or starts after a long stable period.

Seek urgent help for severe lower abdominal pain, fainting, heavy bleeding, or possible pregnancy with pain or bleeding. Arrange prompt advice if you have fever, pelvic pain, unusual discharge, or bleeding after sex. Testing for [Chlamydia](/conditions/chlamydia/) or assessment for [Endometrial Polyps](/conditions/endometrial-polyps/) may be considered when the pattern does not fit pill-related spotting.

Could my pill, missed doses or another medicine explain this? Do I need a pregnancy test or infection test? Should I change the pill or its schedule? How long should I monitor the bleeding?