Question

Once you get vitamin D into your body, either from the sun or from food, it has to do what to get activated?

Answer 1

Vitamin D is activated in two steps: conversion to 25(OH)D in the liver, and further conversion to 1,25(OH)D₂ in the kidneys.

Step-by-step explanation:

Vitamin D is activated in two steps. First, when the vitamin D enters the body, either from the sun or from food, it is converted into 25(OH)D (calcidiol) in the liver. This is the primary form of circulating vitamin D. Then, in the kidneys, 25(OH)D is transformed into 1,25(OH)D₂ (calcitriol), which is the biologically active form of vitamin D.

For example, when sunlight hits your skin, cholesterol present in the epidermis is converted to cholecalciferol (vitamin D3), which enters the blood. In the liver, cholecalciferol is converted to calcidiol, and in the kidneys, calcidiol is further converted to calcitriol.