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What is a Vitamin D test?

Vitamin D plays an important part in calcium metabolism and maintenance of healthy bones and teeth. It has two important forms: 

  • Vitamin D2: It is found in fortified foods (dairy items and cereals)
  • Vitamin D3: It is made by the human body (when exposed to sunlight). Some amount of vitamin D3 is also found in certain foods, such as eggs and fatty fish (salmon, mackerel, etc.). 

Before your body can use them, both these forms get converted to a compound known as 25-hydroxyvitamin D. A vitamin D test measures the levels of 25-hydroxyvitamin D to determine the total vitamin D in your bloodstream.

Abnormal vitamin D levels can indicate the presence of various medical conditions, such as nutritional problems and bone disorders or bone damage.

Alternative names for vitamin D test are ergocalciferol (vitamin D2), calcitriol (1,25-dihydroxyvitamin D), calcidiol (25-hydroxyvitamin D), calcifediol (25-hydroxyvitamin D) and cholecalciferol (vitamin D3).

  1. Why is Vitamin D test performed?
  2. How do you prepare for Vitamin D test?
  3. How is Vitamin D test performed?
  4. What do Vitamin D test results mean?

Vitamin D test is done as a screening test to monitor bone disorders and check vitamin D levels in people with autoimmune conditions and chronic illnesses, like asthma. Doctors typically recommend this test if they observe the following symptoms of vitamin D deficiency:

  • Fractures
  • Weakening of bones
  • Malformation of bones in children
  • Bone softness

Breastfed babies tend to be at a higher risk for vitamin D deficiency if they do not take any vitamin D supplements.
Furthermore, this test is ordered if the following risk factors of vitamin D deficiency are observed:

  • Difficulty in absorbing fat from foods
  • Old age
  • Having a darker complexion
  • Bone disorders, like osteoporosis
  • Lack of sun exposure
  • Obesity
  • Gastric bypass surgery in the past

Vitamin D test does not require any special preparation.

A healthcare professional will withdraw a small amount of blood from a vein in your arm by inserting a needle. The blood sample will be collected in a vial or test tube, which will then be sent to a lab for analysis.
The whole procedure requires about 5 minutes.
There are no significant risks associated with this test. Though some people experience minor bruises or slight pain at the blood withdrawal site, most symptoms disappear soon. If you notice any discomfort, make sure to check in with your doctor at the earliest.

Most laboratories use similar reference intervals even though the method used for vitamin D test differs among laboratories.

Normal results:

As vitamin D toxicity is rare, the focus of this test is to determine the lower limit of total 25-hydroxyvitamin D (D2 + D3), which would indicate vitamin D deficiency.
According to the U.S. Institute of Medicine, 25-hydroxyvitamin D levels of 20 ng/mL or above is sufficient for bone health.

Abnormal results:

As per the Endocrine Society, following are the conditions associated with abnormal 25-hydroxyvitamin D levels:

  • Below 20 ng/mL: vitamin D deficiency
  • 21 to 29 ng/mL: vitamin D insufficiency

Low level of 25-hydroxyvitamin D in the bloodstream may denote the following:

  • Lack of sun exposure
  • Insufficient dietary vitamin D intake 
  • Problems with vitamin D absorption from the intestine

Certain medications can also affect 25-hydroxyvitamin D production in the liver.
A high blood level of 25-hydroxyvitamin D indicates the use of excess nutritional supplements or vitamin pills.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.

Vitamin D Test की जांच का लैब टेस्ट करवाएं

Vitamin D 1 - 25 Dihydroxy

25% छूट + 5% कैशबैक


25% छूट + 5% कैशबैक
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  1. MedlinePlus Medical Magazine: US National Library of Medicine; The challenge of Osteoporosis and brittle bones
  2. Michael F Holick .Evaluation, Treatment and prevention of vitamin d deficiency: an endocrine society clinical practice guideline. The Journal of clinical endocrinology and metabolism. 96. 1911-30. 10.1210/jc.2011-0385.
  3. National Health Service [Internet]. UK; Vitamin D
  4. Center for Disease Control and Prevention [internet], Atlanta (GA): US Department of Health and Human Services; CDC’s Second Nutrition Report Vitamin D deficiency closely related to race/ethnicity
  5. Johns Hopkins Medicine [Internet]. The Johns Hopkins University, The Johns Hopkins Hospital, and Johns Hopkins Health System; Vitamin D and Calcium
  6. National Heart, Lung, and Blood Institute [Internet]. Bethesda: U.S. Department of Health and Human Services; Blood Tests
  7. National Cancer Institute [Internet]. Bethesda: U.S. Department of Health and Human Services; [link]
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