Calcitriol D3 Unit Converter

1,25-Dihydroxyvitamin D3, also known as calcitriol D3, is the D3 component of the calcitriol panel. It is a subcomponent of 1,25-dihydroxyvitamin D (total calcitriol), which is the biologically active hormone form of vitamin D.

Calcitriol D3 is typically the dominant component of total calcitriol and closely approximates the total value unless a patient is taking ergocalciferol (vitamin D2) supplements, in which case the D2 component may contribute meaningfully.

This marker is reported in pg/mL and circulates at very low concentrations compared to 25-hydroxyvitamin D3 (the storage form), which is roughly 1,000 times higher. The two tests measure fundamentally different things and should not be confused.

This value should be interpreted alongside the panel Total (1,25-dihydroxyvitamin D), which is the row that carries a clinical reference range.

Calcitriol D3 is produced primarily in the kidneys, where the enzyme 1-alpha-hydroxylase (CYP27B1) converts 25-hydroxyvitamin D3 (calcidiol) into the active hormone. Smaller amounts are produced by immune cells (macrophages), the placenta, and other tissues.