When should I be worried about periods not starting or being irregular?

An irregular menstrual cycle is common for adolescents in the initial 2 to 3 years, and periods will start to become more regular with age. You should seek advice if your child:

• has not had a period by the age of 15 or within 3 years of breast development

• started having periods but has not had one for 3 or more consecutive months

• continues to have an irregular menstrual cycle after the first 2 to 3 years of menstruating

• has worsening symptoms