Vitamin D 1 25 Dihydroxy Test

1,25-dihydroxyvitamin D2 is the active, hormonally potent form of vitamin D derived from plant and fungal sources (ergocalciferol). A 1,25-D2 test measures this specific form, which is biologically active at very low concentrations. Elevated levels may indicate excessive supplementation, granulomatous diseases (like sarcoidosis), or lymphomas that abnormally produce this hormone. This test is more specialized than standard vitamin D testing and is useful for investigating specific clinical conditions.

1,25-dihydroxyvitamin D is the most biologically active form of vitamin D, produced primarily by the kidneys. This test measures circulating levels of active vitamin D in your blood. Vitamin D is essential for calcium absorption, bone health, immune function, and mood regulation. Low levels may indicate kidney disease, vitamin D deficiency, or calcium disorders, while abnormally high levels can occur with excessive supplementation or certain granulomatous diseases. This test is particularly useful for evaluating bone health and metabolic disorders.

This comprehensive vitamin D panel measures three forms: 25-hydroxyvitamin D (the storage form that indicates overall status), vitamin D2 (from dietary sources), and 1,25-dihydroxyvitamin D3 (the active form). Together, these tests assess vitamin D metabolism and availability. Vitamin D is essential for calcium absorption, bone health, immune function, and mood. Deficiency is linked to weak bones, increased infection risk, and depression.