My endocrinologist switched me to prescription dose Vitamin D2 as my body wasn't responding to D3. Although my levels are finally staying within the range, they are just barely in range and certainly not where she wants them. I have an appointment to see what the next step is. I have autoimmune thyroid disease as well which has been fluctuating in terms of levels. Low D can impact that and I am noticing other things now being impacted. I will be inquiring about taking the Calcitrol blood test, which is not the commonly done one, to see what that may show. I will ask her about adding K2 and/or magnesium.