How Many Days Are There Until Your Next Period?

By Staff WriterLast Updated Apr 6, 2020 10:09:10 AM ET

A regular menstrual cycle starts 28 days after the previous cycle began. The first day of a menstrual cycle is considered to begin on the first day of regular blood flow.

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Menstrual cycles of young teens can be irregular lasting from 21 to 45 days, while the cycles of adults can last from 21-35 days. In general, the first two years of menstruation produce the longest, most irregular cycles. Over time, menstrual cycles normalize and occur after a set amount of time; although, many women never have a 28-day cycle. Birth control pills, weight loss, exercise and ovary disorders can cause irregular cycles.