What is a normal menstrual cycle?

Typically 21–35 days between periods, with 2–7 days of bleeding. Regularity matters more than a specific number. Cycles shorter than 21 days, longer than 35, or with heavy bleeding requiring hourly pad changes need evaluation.

Cycle-to-cycle variation of up to about 7-9 days is considered within normal range for most adult women.

Track for three months before concluding anything. Persistent cycles under 21 or over 35 days, or sudden change from your own pattern, are what warrant assessment.