<prompt> The most potent form of vitamin D isErgocalciferol Vit. D27 dihydroxy cholecalciferol25 dihydroxy cholecalciferol1,25 dihydroxy cholecalciferol  <response>: 1,25 dihydroxy cholecalciferol is the metabolically active form of vitamin D. It helps in the absorption of calcium and phosphorus in the gut, and promotes bone dissolution and mineralization, thereby increasing serum calcium and alkaline phosphatase activity. Ref: Page 127; Ghai essential pediatrics; 6th edition 