Alendronate is often the first drug tried for osteopenia/osteoporosis. It slows bone breakdown by acting on the osteoclasts (the cells that break down old bone) by reducing their numbers. It can help a lot, particularly in the first two to three years. It's not a drug you can take for a long time, though, so you may need something else eventually if it doesn't increase your bone density.

You can also address lifestyle and make sure you are on a nutritionally solid diet (eating minimally processed foods, ensuring you get enough calcium through your diet, eating enough protein, minimizing sugar , etc.) and exercising including resistance (weight) training, and weight bearing activity.

Depending on your T-score, some doctors are going straight to an anabolic drug like Tymlos or Forteo to build lost bone. This is usually when T-scores are lower than -2.5, indicating severe osteoporosis.