Food BestSource Ca+2
Yes, D3 needed for absorption & often ? in US, but best measure vit.
D3 concentration; optimal in the 70-80 ng/ml range. Sun tends to trigger conversion of a little cholesterol in skin to Vit D, then converted in liver to D2 & by kidneys & other tissues to D3. D3 impt for Ca absorption, bone & muscle strength + immune function. Best source food & if D3 conc good, unlikely need Ca+2 supplements