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Clinical definition of the 1, 25 Dihydroxy Vitamin D test

Vitamin D is a fat-soluble vitamin and is absorbed from the intestine like a fat. There are two forms of vitamin D that can be measured in the blood, 25-hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)(2)D].  25-hydroxyvitamin D is the major form of the hormone found in the blood and is the inactive precursor to the active hormone, 1, 25-dihydroxyvitamin D. 1, 25 dihydroxy vitamin D test is done when the calcium is low or the person shows symptoms of vitamin deficiency such as bone malformation in children (rickets) and bone weakness, softness or fracture in adults (osteomalacia).

Why is the 1, 25 Dihydroxy Vitamin D test done?

1, 25- hydroxy vitamin D test is carried out to identify possible deficiency in vitamin D and monitor individuals with diseases that interfere with fat absorption, such as cystic fibrosis and Crohn’s disease, and in patients who have had Gastric bypass surgery and may not be able to absorb enough Vitamin D.

What are the common signs/symptoms when the 1, 25 Dihydroxy Vitamin D test is done?

  • Poor mineralization of bones
  • Fractures, teeth problems
  • Bone pain and tenderness
  • Bow legs or knock knees
  • Curvature of the spine
  • Poor muscle development and tone
  • Impaired growth and delayed walking in children
  • Lower than normal bone mass

Who should do the 1, 25 Dihydroxy Vitamin D, serum test (Target population)?

Persons showing the above signs & symptoms of bone weakness.

What should I do before the 1,25 Dihydroxy Vit D serum test?

Specimen type Specimen collection procedure Preparatory instructions before the test *
Serum (Blood Sample)



Collection of blood from a vein, usually from the arm

No Fasting Required.

No other special preparations required.

*Subjects suffering from any illness or on oral or injectable medications are advised to consult their physician prior to requesting any tests or procedures.

How do I interpret my 1,25 Dihydroxy Vit D serum test results?

Reference Range* Interpretation
19.6 to 54.3 pg/ml ** Normal

‘*A Reference range is a set of values which helps the healthcare professional to interpret a medical test. It may vary with age, gender, and other factors. Reference ranges may also vary between labs, in value & units depending on instruments used and method of establishment of reference ranges’

Diseases/conditions related to the 1, 25 Dihydroxy Vitamin D serum test

  • Hypervitaminosis D
  • Sarcoidosis
  • Rickets
  • Osteomalacia
  • Multiple sclerosis
  • Arthritis
  • Osteoporosis
  • Lymphoma
  • Osteopenia

Other tests related to the 1, 25 Dihydroxy Vitamin D serum test

  • Calcium
  • Phosphorus
  • Parathyroid Hormone (PTH)
  • Magnesium