Vitamin D Test

What is Vitamin D test? 

Cholecalciferol is called vitamin D3 and is a form of Vitamin D. It transforms into a hormone in the bloodstream and helps in the absorption of calcium and phosphate. It is an essential nutrient needed by the body for the maintenance of healthy bones and teeth and also overall health. Vitamin D3 helps the kidneys recycle phosphate back into the bloodstream, leading to the appropriate balance of pH levels. It also helps in the treatment of underactive parathyroid glands. 

There is a primary difference between vitamin D2 and D3; it is that vitamin D2 is obtained from dairy products and other food sources, while vitamin D3 is naturally made by the body when the body is exposed to sunlight and is therefore called the "sunshine vitamin."

What are the other names for the Vitamin D test? 

The other names are 25-hydroxyvitamin D, 25(OH)D, Cholecalciferol test, Ergocalciferol test, calcidiol test, vitamin D2 test, and vitamin D3 test.

What are the test parameters included in the Vitamin D test?

There is only one parameter.

What does the Vitamin D test measure? 

Vitamin D is necessary for maintaining good health. It helps the body to absorb minerals like calcium, magnesium, and phosphorus from the diet. It also helps to maintain proper levels of calcium, phosphate, and parathyroid hormone in the blood.

Vitamin D plays a very important role in helping the body absorb calcium, which makes it crucial for maintaining bone health. Inadequate levels of vitamin D may lead to abnormal bone development, bone weakness, and pain.

It is unlikely that other vitamins, like Vitamin D, can be created in the human body. When your skin is exposed to direct sunlight or ultraviolet radiation, it converts a chemical in the skin into an active form of vitamin D. Vitamin D may also be obtained through the diet, including from fortified or vitamin-enriched foods and vitamin supplements.

There are two types of Vitamin D:

• Vitamin D2 (ergocalciferol): Vitamin D2 is produced in plants, such as yeast or mushrooms. This is also available as a supplement and in fortified foods.

• Vitamin D3 (cholecalciferol): Vitamin D3 (Vit D3) is produced in the skin when it is exposed to sunlight. It is also found in some animal-based foods and can be consumed in certain fortified foods or dietary supplements.

Usually, both vitamin D2 and D3 need to undergo chemical changes before being able to be used by the body. These changes occur in the liver and the kidneys and convert vitamin D into measurable substances called 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D:

• 25-hydroxyvitamin D: In the liver, vitamin D will be converted into 25-hydroxyvitamin D, which is also called 25(OH)D. Most of the time, vitamin D levels will be tested by analysing blood levels of 25(OH)D. Testing at 25(OH) D is considered the most accurate way to analyse how much vitamin D is in your body because 25(OH) is the major form of vitamin D that is circulating in the bloodstream.

• 1,25-dihydroxyvitamin D: In the kidneys, 25 (OH) D is converted into a hormone called active vitamin D or 1,25-dihydroxy vitamin D. Sometimes, laboratories can check the blood level of 1,25-dihydroxy vitamin D, which is also called 1,25(OH)2D. This substance is generally not used to determine inadequate vitamin D levels, but it can be measured in patients with abnormal calcium levels or kidney problems.   

What’s the normal range of Vitamin D? 

Deficient - <20 ng/mL / (<50 nmol/L)

Insufficient - 20 – <30 ng/mL / (50 – <75 nmol/L)

Sufficient - 30 –100 ng/mL / (75 – 250 nmol/L)

Potential Toxicity - > 100 ng/mL / (> 250 nmol/L)

Who should get a Vitamin D test? 

A Vitamin D test is recommended to determine if a deficiency, insufficiency, or toxic level of vitamin D is present or to monitor the treatment for a previously diagnosed deficiency.

The doctor might recommend a vitamin D blood test for you if you are experiencing symptoms of a vitamin D deficiency, such as:

• Weakening of the bones

• Abnormal bone development

• Bone deformity

• Bone pain

• Muscle weakness or cramps

• Seizures

• Dental abnormalities

Sometimes, vitamin D tests are used as screening tests for individuals at increased risk of deficiencies. These screening tests are conducted before any symptoms occur. The following factors can increase the risk of developing a vitamin D insufficiency or deficiency:

• Age over 65 years

• Obesity

• History of weight loss surgery

• Osteoporosis

• Reduced ability to make vitamin D in the skin due to limited sun exposure, sunscreen use, or dark skin pigmentation

• Digestive diseases which make it difficult to absorb nutrients from food, including celiac disease and Crohn’s disease

• Kidney and liver diseases

• Use of certain medications

A vitamin D test can also be recommended if the doctor suspects that you may have abnormally high vitamin D levels, known as vitamin D toxicity. This may occur as a result of taking too much vitamin D in supplements rather than from too much sun exposure or dietary intake.

Excess vitamin D in supplement form might cause your body to absorb more calcium from food and to reabsorb calcium from the bones into the blood. This results in excess calcium in the food, also known as hypercalcemia, which may lead to symptoms like fatigue, confusion, bone pain, nausea and vomiting, frequent urination, and kidney problems.

The doctor who is familiar with your medical history is in the best position to determine whether you may benefit from vitamin D testing.

Are there any preparations needed for the Vitamin D test?

No special preparation is required and fasting is not required.