Why is my period irregular?
Last updated September 3, 2026.
Some variation is normal - 28 days is an average, not a rule, and shorter or longer cycles can still be healthy. Beyond the normal spread, the usual suspects are stress, sudden weight change, hard training, PCOS, thyroid problems, perimenopause, and birth control changes. The pattern matters: always-irregular suggests something structural like PCOS; newly-irregular suggests a change worth checking.
What to do
- Track for a few months. An app or calendar note turns "it feels off" into a pattern a doctor can read.
- Rule out pregnancy first. A late or absent period in anyone sexually active starts with a test.
- Note what changed. New stress, weight change, training load, or a birth control switch are the obvious levers.
- See a doctor for persistence. Three-plus off cycles, months without a period, or bleeding between periods earns a workup.
Related questions
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