VITAMIN D, 1,25 DIHYDROXY, SERUM

Vitamin D, 1,25 Dihydroxy, Serum

What it is

The Vitamin D, 1,25 Dihydroxy, Serum test measures the level of calcitriol, the active form of vitamin D, in the blood. Unlike the 25-hydroxy vitamin D test (used to assess overall vitamin D status), this test evaluates how well the kidneys are converting vitamin D into its biologically active form. It plays an important role in regulating calcium, phosphorus, and bone health.

Uses

This test is used to investigate kidney function, evaluate calcium or phosphorus imbalances, and diagnose certain metabolic bone diseases. It is often ordered when disorders such as chronic kidney disease, parathyroid gland dysfunction, or rare genetic conditions affecting vitamin D metabolism are suspected.

Symptoms That May Lead to the Test

Doctors may recommend this test if you have unexplained bone pain, frequent fractures, muscle weakness, abnormal calcium or phosphorus levels, or symptoms suggestive of parathyroid or kidney disorders. It may also be ordered in cases of rickets, osteomalacia, or certain rare metabolic conditions.

Abnormal Results

Low 1,25 Dihydroxy Vitamin D: May suggest chronic kidney disease, hypoparathyroidism, or genetic disorders affecting vitamin D metabolism. Low levels can lead to weak bones, softening (osteomalacia), or rickets in children.

High 1,25 Dihydroxy Vitamin D: May indicate hyperparathyroidism, sarcoidosis, certain lymphomas, or excessive vitamin D intake. High levels often cause elevated calcium, which can result in kidney stones, nausea, confusion, or abnormal heart rhythms.

Risks

The test requires a standard blood draw, which has minimal risks such as mild pain, bruising, or dizziness. Serious complications are rare.