[elric]

Is the blood level diagnostically significant with vit D? Or is this something like magnesium where serum levels can be normal while having a magnesium shortage? IIRC vit d is fat soluble, does the body store any excess quickly, or does it linger around?

[canucker2016]

Yes, from https://pmc.ncbi.nlm.nih.gov/articles/PMC5577589/

  The goal of this study was to investigate whether the relationship between body composition, serum 25-hydroxyvitamin D (25OHD), vitamin D in subcutaneous (SQ) and omental (OM) adipose, and total adipose stores of vitamin D differ among OB and C. ... In summary, although OB had significantly greater total vitamin D stores than C, the relationship between serum 25OHD and fat vitamin D and the overall pattern of distribution of vitamin D between the OM and SQ fat compartments was similar.