25-hydroxyvitamin D, Serum

25-hydroxyvitamin D, Serum

What is the 25-hydroxy vitamin D test?

Vitamin D is vital for strong bones by helps your body to absorb calcium. It also has important roles in immune function and cancer prevention. Similarly, vitamin D toxicity can cause serious hypercalcemia if overmedication.

First your body converts vitamin D to a chemical known as 25-hydroxyvitamin D, also called calcidiol.

The 25-hydroxy vitamin D test is perform to monitor vitamin D levels in blood. The test can determine if your vitamin D levels are too high or too low in your body.

Vitamin D consists of two bioequivalent forms:

Vitamin D Forms Sources
Vitamin D2 Vegetable sources
Vitamin D3

1. Endogenous synthesized from cholesterol through sun exposure

2. Eexogenous from animal diet


Formal Name:

  • 25-hydroxyvitamin D
  • 1,25-Dihydroxyvitamin D, Serum

Also known as:

  • Ergocalciferol (Vitamin D2)
  • Cholecalciferol (Vitamin D3)
  • Calcidiol (25-hydroxyvitamin D[25(OH)D])
  • Calcifidiol (25-hydroxy-vitamin D)
  • Calcitriol (1,25 dihydroxy-vitamin D)


Why is a 25-hydroxy vitamin D test done?

Your doctor may order Vitamin D test if you have symptoms of Vitamin D deficiency:

  • Fatigue or tiredness
  • Bone and back pain
  • Muscle pain
  • Depression
  • Bone weakness & bone softness
  • Bone malformation (in children)
  • Fractures
  • Hair loss
  • Older adults
  • Obesity
  • Gastric bypass surgery
  • Intestines diseases such as Crohn's disease


Related tests:

  • Calcium
  • Phosphorus
  • PTH
  • Magnesium
  • Bone Markers
  • Trace Minerals


3.Useful for:

Assessment of vitamin D, especially in patients with renal disease Investigation of some patients with clinical evidence of vitamin D deficiency (eg, vitamin D-dependent rickets due to hereditary deficiency of renal 1-alpha hydroxylase or end-organ resistance to 1,25-dihydroxy vitamin D) Differential diagnosis of hypercalcemia.

Confirming a diagnosis of 3-beta-hydroxy dehydrogenase (3-beta-HSD) deficiency.

Analysis for 17-hydroxypregnenolone is also useful as part of a battery of tests to evaluate females with hirsutism or infertility; both can result from adult-onset CAH.

4.Clinical Importance:

Vitamin D comes from two sources: endogenous, which is produced in the skin on exposure to sunlight, and exogenous, which is ingested in foods and supplements. The chemical structures of the types of vitamin D are slightly different, and they are named vitamin D2 (ergocalciferol, which comes from plants) and vitamin D3 (cholecalciferol, which comes from animals). The D2 form is found in fortified foods and in most vitamin preparations and supplements. Vitamin D3 is the form produced in the body and is also used in some supplements. Vitamin D2 and D3 are equally effective when they are converted by the liver and the kidney into the active form, 1,25-dihydroxyvitamin D.

Some tests do not distinguish D2 and D3 forms of the vitamin and report only the total result. Newer methods, however, may report levels of both D2 and D3 and then add them together for a total level.

The main role of vitamin D is to help regulate blood levels of calcium, phosphorus, and (to a lesser extent) magnesium. Vitamin D is vital for the growth and health of bone; without it, bones will be soft, malformed, and unable to repair themselves normally, resulting in diseases called rickets in children and osteomalacia in adults. Vitamin D has also been shown to influence the growth and differentiation of many other tissues and to help regulate the immune system. These other functions have implicated vitamin D in other disorders, such as autoimmunity and cancer.


25-hydroxyvitamin D Test Sample Type, Quantity, Storage & Timing

Primary Sample Blood
Sample Quantity 2 ml
Sample storage Refrigerator
Test Timing 2 hours



Vitamin D Test Preparation

Inform your doctor if you are on any medications, have underlying medical conditions before your Vitamin D test.


The patients don't need any special preparations required for the Vitamin D test.


Fasting is not required before the sample collection for the Vitamin D test.


Are there any risks to the 25-hydroxyvitamin D Test?

There is very little risk including oozing at the draw site, bruising or mild tenderness at the site, to having a blood test.


You may have a slight bruise or pain at the spot where the needle was put in, but most symptoms go away very quickly.


25-hydroxyvitamin D Testb Result Interpretation

High Level Low Level
Sarcoidosis Chronic renal failure
Some malignancies Hypoparathyroidism
Primary hyperparathyroidism  
Physiologic hyperparathyroidism  


Vitamin D normal range (Reference Values) :

Gender Age Value
Male <16 years 24-86 pg/mL
Male >=16 years 18-64 pg/mL
Female <16 years 24-86 pg/mL
Female >=16 years 18-78 pg/mL


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