Active vitamin D test (calcitriol)

What this test is

This is a different vitamin D test from the usual one. Most vitamin D tests check a form called 25-hydroxy vitamin D. That form best shows how much vitamin D your body has stored. This test checks a different, more active form instead. Other hormones control this form closely. So it can look normal even when your vitamin D is actually low. Because of this, it is not a good way to check your vitamin D level. It is used for a few rare problems instead. Most of these involve the kidneys or calcium levels. A specialist is often involved in that workup. If you just want to know your vitamin D level, ask for the standard 25-hydroxy vitamin D test.