Active vitamin D
Healthy kidneys make a hormone called calcitriol, the active form of vitamin D. Calcitriol helps your gut absorb calcium from the food you eat. When your kidneys fail, they make less calcitriol. This means you can't absorb as much calcium, even if you eat more foods that have it. If your calcitriol blood levels drop, your body will pull calcium out of your bones.
What's Calcitriol, Anyway?
Your body gets vitamin D in two ways: from foods you eat—like dairy products and fortified bread—and from sunshine on your skin. Your liver and kidneys convert vitamin D into an active form, the hormone calcitriol. A hormone is a chemical signal made in one part of the body that acts on another part. Calcitriol tells your gut to absorb calcium from your food.
