I had blood work done last August and I was low in vit D. PCP started me on high dosage vit D for 12 weeks. I found out after I finished that I was doing Vit D2 which is not what should be given as a supplement! She advised that I do 2000IU everyday after that, and I actually started with 4000IU. I have been pretty diligent about it and had some work done again last week, and vit D is stll low! I have no idea why...would love to hear if there have been BTDT. thanks.