What is Vitamin D Test? Procedure, Uses and Results of Vitamin D Test

What is Vitamin D Test? Procedure, Uses and Results of Vitamin D Test

Vitamin D is an extremely important nutrient that is produced by the body when it is exposed to the ultraviolet rays of the sun. But, there are very few food sources of vitamin D, therefore, doctors often suggest vitamin D supplements to patients with vitamin D deficiency. Vitamin D is required by the body for absorption of calcium in the intestine and maintenance of adequate serum calcium and phosphate concentrations for normal mineralization of bones. Vitamin D is also required for bone growth and reducing the risk of osteoporosis. But, it has been noticed that a considerable share of the population is deficient in vitamin D, but the only way to confirm it is to perform a Vitamin D Test which helps to determine the level of vitamin D in the body.

25-Hydroxy Vitamin D Test

25-hydroxy vitamin D test is the most effective method for measuring the level of vitamin D in a person’s body. 25-hydroxy vitamin D (25OHD) is the main circulating form of vitamin D which is the precursor of the active form (1,25-dihydroxyvitamin D). The long half-life of 25-Hydroxy Vitamin D makes it it readily available for determining the vitamin D levels in patients.

Vitamin D is available in two main forms – vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol). Vitamin D3 is derived from animal products and vitamin D2 is obtained from vegetable sources. Both forms of vitamin D are metabolized to their respective 25OHD forms (25OHD3 and 25OHD2). Therefore, vitamin D test can accurately quantify both forms of vitamin D which is essential for diagnosis of vitamin D disorders and monitoring of patient’s response to treatment.

Uses of a Vitamin D Test

A vitamin D Test usually helps with the following conditions:

  • Determines the cause of bone weakness, bone malformation or abnormal calcium metabolism
  • Helps to diagnose and monitor the problems with the functioning of the parathyroid gland, because parathyroid hormone is integral for vitamin D activation
  • Monitor the health statuses of patients with diseases and conditions that interfere with fat absorption such as cystic fibrosis, because vitamin D is a fat-soluble vitamin that is absorbed from the intestines just like fat
  • Determines the effectiveness of treatment that includes vitamin D, calcium, phosphorus and magnesium supplementation

Who are Ideal Candidates for 25-Hydroxy Vitamin D Test?

The doctor may recommend a 25-Hydroxy vitamin D test for a number of reasons. First, this vitamin D test may help to determine whether there is excess or deficiency of vitamin D that is causing bone weakness or other abnormalities. It can also work as a monitor for people who are at high risk of having vitamin D deficiency. Those who should get a vitamin D test include:

  • People who don’t get much exposure to sun light
  • Older adults
  • People suffering from obesity
  • Babies who are dependent only on breastfeeding
  • People who have undergone gastric bypass surgery
  • People with disease of the intestines – Crohn’s disease
  • People receiving therapy to prevent or treat osteoporosis
  • Patients with symptoms of hypocalcemia or hypercalcemia
  • Children with suspected rickets
  • Adults with suspected osteomalacia

How the 25-Hydroxy Vitamin D Test is done?

  • The patient might be asked to fast for 4 to 8 hours before the test
  • The 25-Hydroxy Vitamin D test involves a common blood test
  • During the test, the lab technician draws a blood sample from a vein in the patient’s arm using a needle
  • The sample is then tested in the lab for the precise level of vitamin D

Results of a 25-Hydroxy Vitamin D Test

The result of vitamin D test depends on a number of factors such as age, gender and use of specific testing method. There are no specific number range that indicates vitamin D deficiency. The Endocrine Society determines vitamin D deficiency as a 25-hydroxyvitamin D blood level below 20 ng/mL (50 nmol/liter) and vitamin D insufficiency as a level between 21–29 ng/mL (52.5–72.5 nmol/liter).

Low blood level of 25-hydroxy vitamin D means:

  • The patient is not eating a balanced and complete diet
  • The patient’s intestines are not absorbing vitamin D to the fullest
  • The patient is not spending enough time in the sunlight
  • Vitamin D deficiency can also indicate higher risk of certain cancers, immune diseases and cardiovascular disease

High levels of vitamin D in the blood usually results from excessive intake of vitamin D supplements and other nutritional supplements containing vitamin D. High levels of vitamin D can lead to hypervitaminosis D that increases the risk of liver and kidney disorders. High levels of vitamin D cannot be caused by consuming vitamin D rich foods or excessive sun exposure.

Health Risks Related to Vitamin D Deficiency

A lack of vitamin D in the body can lead to some serious health issues:

Prostate Cancer:

There is a strong link between low blood levels of vitamin D and increased risk of prostate cancer. Research shows that the risk increases almost 4 to 5 times in men with low vitamin D levels. The reason isn’t yet understood by researchers are saying that testing for vitamin D deficiency and treating it may be an important part of cancer care.

Dementia and Alzheimer’s disease:

People with moderate deficiency of vitamin D have a 53% increased risk of developing dementia. Deficiency of vitamin D is also associated with 122% increase in risk of Alzheimer’s disease. Researchers believe that vitamin D helps to clear the plaques that form in the brain that are linked to dementia.

Speeds Up Multiple Sclerosis:

Previous research found that low levels of vitamin D are associated with increased risk of neuromuscular disorders such as Parkinson’s disease and Multiple Sclerosis. Recent research suggests that if a person already has multiple sclerosis, vitamin D deficiency make things worse by speeding up the progressing of the disease. Administering adequate levels of vitamin D in early-stage multiple sclerosis patients reduced the risk of new brain lesions by 57%.

Severe Heart Disease:

People suffering from vitamin D deficiency have 32% increased risk of coronary artery disease compared to those who have normal levels of vitamin D. Vitamin D deficiency affects multiple blood vessels. Vitamin D reduces the risk of heart disease by controlling inflammation.

If your doctor has already recommended a Vitamin D Test and you are worried about the results, then discuss the same with your doctor in order to understand the exact cause of your deficiency and treat it accordingly.

Medically Reviewed By
Dr. Sameer Kumar (MBBS, MS, FMAS, DMAS)Obstetrician & Gynecologist