Ovarian reserve naturally declines with age, but low ovarian reserve does not always mean ovarian insufficiency. While ovarian insufficiency (whether premature or age-related) is marked by extremely low levels of ovarian reserve markers, having low ovarian reserve at a young age does not necessarily mean a woman will experience early menopause.  

Currently, there are no standardized "normal" ranges for ovarian reserve markers like Antral Follicle Count (AFC) and Anti-Müllerian Hormone (AMH) across all age groups. Some women have lower-than-average ovarian reserve markers but continue to have regular menstrual cycles and normal ovarian function.  

A key distinction is that a woman with regular menstrual cycles is not considered to have ovarian insufficiency, even if her ovarian reserve is lower than expected. However, in some cases, women with very low ovarian reserve markers may stop having periods before the age of 40, leading to a diagnosis of premature ovarian insufficiency (POI).