It is absorbed with dietary fat, reach blood
stream via lymphatic system
the first type (cholecalciferol) vitamin D3.....
is main form in man, being synthesised in the skin under the action of ultraviolet light
the second type (ergocalciferol) vitamin D2.....
is the main form ingested in the diet primarily from plants.
Neither form is biologically active until it is converted in the liver to the 25-OH derivative,and this to the 1,25(OH)2
derivative in the kidney