Description

Vitamin D, 1,25-Dihydroxy—also known as calcitriol—is the active form of vitamin D in the body. It plays a critical role in maintaining proper calcium and phosphate balance, supporting bone health, nerve signaling, and muscle function. This form of vitamin D is mainly produced in the kidneys and is tightly regulated by hormones like PTH (parathyroid hormone).

Why the Vitamin D, 1,25-Dihydroxy Test Is Important

A blood test for 1,25-dihydroxyvitamin D helps detect or monitor:

  • Kidney Function Issues – The kidneys activate vitamin D. Low levels may indicate impaired kidney function, while high levels may suggest overproduction due to other causes.
  • Calcium Metabolism Disorders – Conditions like hypercalcemia (high calcium) or hypocalcemia (low calcium) can be related to abnormal vitamin D metabolism.
  • Granulomatous Diseases – Disorders such as sarcoidosis or tuberculosis may cause elevated 1,25(OH)₂D due to excess production outside the kidneys.
  • Genetic Disorders or Rickets – Some rare inherited conditions affect how the body uses vitamin D, and this test can help identify those abnormalities.

High or low levels of active vitamin D can offer important insights into the causes of bone weakness, calcium imbalance, and other metabolic disturbances.

Fasting: Not required.