Synonyms: Cholecalciferol Metabolite; 25-Hydroxycalciferol; 25-OH-D; Vitamin D3 Metabolite

This is not the same as calcitriol or 1,25 dihydroxy vitamin D3. Calcitriol must be ordered separately 

Why It Is Done

Determine if a patient has a deficiency or excess of vitamin D.

A number of studies have shown that vitamin D deficiency is very common, 75% of women and 51% of men have been found to have insufficient levels of Vitamin D.

A high number of older men and women are deficient in Vitamin D -putting them at risk for muscle weakness and poor physical performance.

This situation has occurred, in part, because the foods in the typical American diet are very low in vitamin D. Fatty fish, such as mackerel and salmon and fish liver oils, are some of the few natural dietary sources of vitamin D. In the US, vitamin D is added to milk. Unfortunately, too many children do not drink enough milk to raise their vitamin D levels to the optimum range. The level of Vitamin D in fortified milk is frequently much lower than that recommended by the FDA. Human milk contains very little vitamin D because many mothers are deficient, so children of mothers who choose to breast-feed are at risk of developing disease if they are not given supplemental vitamin D.

Test Overview

25 hydroxy vitamin D is the most accurate measure of vitamin D stores in the body.

25 hydroxy vitamin D is stored in the liver where it is converted from other forms of vitamin D, either obtained from the diet or made in the skin by sunlight.

25 hydroxy vitamin D is then changed to its active form, 1,25 dihydroxy vitamin D in the kidney. This active form of vitamin D causes increases in calcium and phosphate by activity primarily on the intestines, kidney and bone.

This is not the same as calcitriol or 1,25 dihydroxy vitamin D3. Calcitriol must be ordered separately

How To Prepare

No special preparation needed.