It makes a difference with CTX, not so much with P1NP, but we all do them together so basically both are done fasting. For CTX I was told to do it early (7-8am) and at a consistent time. @koleke glad your doc reordered.

One reason these tests might be seen as unreliable by some docs is apparently that they are done at different times and with and without fasting. McCormick says they are reliable if done right. My main endo doesn't use them because they "don't tell everything that is going on in bones." There are other tests as well, alkaline phosphatase, calcium, PTH etc. I am not sure myself. I get the tests done but I don't rely on them because they don't match my expectations or DEXA.