What counts as irregular periods?
Short answer: Irregular periods are menstrual cycles that vary widely in timing, flow, or duration compared with a person’s typical pattern. Examples include cycles consistently shorter than 21 days or longer than 35 days, missed periods for several months, very heavy or very light bleeding, or unpredictable spotting between cycles.
Explanation
Menstrual regularity is usually assessed by cycle length, bleeding amount, and predictability. A typical cycle ranges about 21–35 days; variation of more than about 7–9 days cycle-to-cycle is considered irregular. Specific definitions include oligomenorrhea (infrequent cycles, >35 days), polymenorrhea (frequent cycles, <21 days), amenorrhea (absence of menstruation for three months or more if previously regular), and menorrhagia (excessive bleeding). Irregularity can be normal during adolescence and perimenopause. Common causes include pregnancy, breastfeeding, polycystic ovary syndrome (PCOS), thyroid disorders, hormonal contraception changes, significant weight loss or gain, extreme exercise or stress, and some medications or medical conditions. Evaluation usually involves cycle tracking, pregnancy testing if applicable, basic labs (pregnancy test, thyroid function, prolactin) and pelvic exam or ultrasound when indicated.
Tips
- Track cycle length, bleeding days, and symptoms for at least three months.
- See a healthcare provider if cycles are <21 or >35 days, absent for 3+ months, or if bleeding is very heavy or prolonged.
- Take a pregnancy test if sexually active and a period is missed.
- Review medications and recent weight, stress, or exercise changes with your clinician.
- Ask about tests for PCOS, thyroid function, and prolactin if irregularity persists.
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