At what age is bone density usually at its highest?

In both men and women, bone density reaches its peak at approximately 30 years of age.12

Following this period of peak density, bone mass typically begins a slow, gradual decline. In women, this process of bone loss accelerates significantly at the onset of menopause due to the associated decrease in the production of estrogen and other sex hormones. While the rate of loss eventually slows after the initial postmenopausal years, the decline continues indefinitely, contributing to an increased risk of osteoporosis and fractures in later life.321