Bone density can look at calcium deficiency, and reduced bone mass means calcium deficiency, because only calcium deficiency can lead to osteoporosis and reduced bone density. If the T value is between minus 1 and minus 2.5, it means that the bone mass is decreasing, so you need to take calcium supplements and vitamin D. In addition, you can maintain the existing bone mass by getting more sunlight and exercising more. If the bone mass continues to decrease below minus 2.5, it means that medication is needed, including calcium and vitamin D. In addition, antiosteoclastic drugs such as alendronate can be taken to alleviate the loss of bone density and maintain the existing bone mass level.