Significant variability or erratic changes in menstrual cycle length may indicate underlying issues and warrant discussion with an OB/GYN.

“So if you're somebody who's consistently had 23 day long cycles and all of a sudden you're having 30 day long cycles, that's not necessarily an indication of anything bad. But if it's 21 days one month and it's 30 days the next month and it's 17 days the next month or even if it's always falling within that 21 to 35 day long cycle but it's very variable from each month or every other month or so, you probably want to talk to your OB/GYN because that could indicate a number of different things.”