Most Common Cause of Irregular Periods

When ovulation does not happen regularly, bleeding may come early, late, or not at all in a cycle. The pattern can also change after starting or stopping hormonal contraception, during the years leading up to menopause, or after major changes in exercise, weight, sleep, or emotional strain.

Anovulation commonly presents as irregular or absent bleeding because the ovary is not releasing an egg in a predictable pattern. Polycystic ovary syndrome can also present with irregular periods, sometimes alongside acne, increased facial or body hair, or difficulty conceiving. Perimenopause commonly presents with cycles that become less predictable as ovarian hormone patterns change.

Less common explanations include premature ovarian insufficiency, thyroid problems, high prolactin, some medicines, and pregnancy. A late period has more than one possible explanation, so the timing and accompanying symptoms matter.

Track the first day of each bleed, how long it lasts, how heavy it is, and symptoms such as pelvic pain, hot flushes, acne, or unusual hair growth. Note recent changes in contraception, medicines, stress, exercise, sleep, and weight. If pregnancy is possible, take a pregnancy test.

A clinician may review your history, check for pregnancy, and decide whether examination or blood tests are useful. Treatment depends on the cause and your goals. Options may include treating an underlying condition, regulating bleeding with a combined pill, or using metformin for PCOS when clinically appropriate.

Arrange a medical review if irregular bleeding continues, periods stop unexpectedly, cycles change after being regular, or you have difficulty becoming pregnant. Seek prompt care for very heavy bleeding, severe or one-sided pelvic pain, faintness, or bleeding during pregnancy.

Urgent symptoms are assessed by their severity, not by whether irregular periods are common. If you feel weak, short of breath, confused, or unable to stand safely because of bleeding or pain, seek urgent medical help.

Ask what pattern your cycle suggests, whether pregnancy or a hormone-related cause should be checked, and whether your symptoms fit anovulation, perimenopause, or polycystic ovary syndrome. You can also ask which treatment matches your bleeding pattern, pregnancy plans, and medical history.