Which is the safest osteoporosis treatment that builds bone and prevents fractures, without causing problems to the kidneys?

Healthy lifestyle. Take calcium and vitamin d supplementation as advised by a doctor who knows your condition. Exercise is all important and use of one of those small round in-the-home floor trampolines can be useful if gently and regularly undertaken. We have strong bones to hold up our body tower within the gravitational field. If you magnify the field, your bones will accommodate.
Hard to say . Exercise and vit d probably would have no sig effect negatively on kidneys fosamax and it's cousins don't affect kidneys much forteo and Prolia also not any sig problems re kidney that i know right off hand.
Only forteo builds. Forteo is the only drug that induces bone formation. The others prevent bone loss, although that allows the bones to become stronger over time, too. None of the meds damage the kidneys, but the bisphosphonates (like fosamax) can't be used in someone who has kidney dysfunction.