Irregular cycles

Cycles are usually considered irregular when they are shorter than 21 days, longer than 35 days, or vary by more than about seven to nine days between cycles. Irregularity often reflects irregular ovulation and is a reason to see a GP earlier rather than waiting a full 12 months of trying.

Also known as: irregular periods, unpredictable cycles

Last reviewed: 10 September 2026. Written by the Antega Editorial Team. General information only — always follow the advice of your own clinic, doctor or pharmacist.