What counts as a normal menstrual cycle length?
Answered by the AskDoc Medical Team · Medically reviewed under our Medical Director, MBBS
Textbooks say 28 days; bodies say 21 to 35, counted from the first day of one period to the first day of the next. A few days of variation between cycles is ordinary.
Consistency is your baseline: a shift of more than a week from your usual, cycles suddenly shorter than 21 days or beyond 35, or skipped months deserve attention.
Tracking three cycles in any app or diary gives you and any doctor the fastest useful picture ever brought to an appointment.
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