Why would a 15 year old be bleeding between periods?

Bleeding between periods, known as intermenstrual bleeding, can occur in a 15-year-old due to various reasons, such as hormonal fluctuations, stress, or changes in weight. It may also be a sign of an underlying condition, such as polycystic ovary syndrome (PCOS) or an infection. If the bleeding is persistent or accompanied by other concerning symptoms, it's important for the teenager to consult a healthcare professional for evaluation and guidance.