i was able to see changes annually with bone density tests annually

@me49 If you don't see changes it would be because your bones haven't changed very much. That could be good in some situations or bad in others. If you are taking an anabolic like Evenity and you do not have a change on your DXA in the one year on the med then that is bad. You want that bone growth. If you wait two years to check and see the results of one year on Evenity then you will not know for sure what Evenity did for you. The effect of the Evenity will be mixed up with the effect of the follow up drug or with whatever bone loss you have if you don't use a follow up med. You won't know whether you might want to try Evenity again in the future.

Also what if you are losing bone. My bone density has been going down for years. In one 16 month period I lost almost 10% in both my total hip scores. Knowing that spurred me to action. There can be lots of change in bone for good or bad in one year. I'm not saying everyone needs a DXA every year, not at all, but depending on your individual situation a scan every year may be just what's needed.

The studies done on these meds sometimes do DXA's at 6 months then again at a year. For that matter studies on exercise programs will do DXA's at anywhere from 6 months to a year. The LIFTMOR studies done in Australia showing good bone growth with an resistance exercise program measured bone density with DXA's at 8 months. Bone markers may be used in these studies in addition to the DXAs but they cannot replace the DXA.

The reason we hear this "you only need a scan every two years" is to save money. It is not a recommendation made with an individuals best interest in mind.