Mike- much depends on the skill of the practitioner. Since this vitamin d issue is unknown by most, you would also have to first educate the tester on what to look for. I had to read the marshall articles for days to fully grasp it. you compare the levels of the various vit d forms in the body, and look for the patter marshall identifies. or, check and see whether your VDR's are clear and operating normally. all of this came out exactly as marshall describes for me. So i put up with the abuse from the vit d heads, because I know better. and I know how dangerous this is. and I know that almost no one out there is really going to tell them about this. certainly not the vid d council.