I don't know for sure but usually doctors start off with an oral medication. There's a "pecking order" with meds where insurance may not cover a more expensive injectable or infusion unless you failed to tolerate the first line drug.

In my case I had mild osteoporosis 2 years ago and chose to start with Boniva, not Fosamax. My regular PCP prescribed it. They are both the same class but Boniva is once a month and Fosamax is once a week. I had gastritis after 4 months and went off it.

After I went off the Boniva, I told my PCP that I would hold off on seeing a specialist until after my next Dexa scan and that I would take calcium supplements to see if that helped. It didn't. My follow up Dexa showed severe osteoporosis. My scores had deteriorated significantly just in 2 years. I was referred to a rheumatologist at that point. The rheumatologist prescribed Evenity. I'm taking it without any issue.