hi, dale. Bone markers measure residue in your blood or urine that is left by cells called osteoblasts building bone and the residue left by cells called osteoclasts that disintegrate the bone.
The most common and (I think) most reliable are P1NP for the building cells and CTX for the disintegrating cells.
These tests can be used to determine whether a medication is effective for you, so that you don't have to wait for dexa results.
Oral bisphosphonates have been the mainstay against osteoporosis, and are commonly given to patients whose T scores are under -2,5. There are injectable bisphosphonates zoledronate in the form of Reclast and Zoloft. They can deliver a higher dose because much of the oral dose is lost in the stomach. Then there are the anabolic injectables Tymlos, Forteo, Evenity--thought to be half anabolic and half antiresorptive. And finally Prolia which is antiresorptive through a different mechanism than the bisphosphonates.