Vitamin D is a fat-soluble vitamin that is essential for maintaining healthy bones and teeth. It plays a key role in the regulation of calcium and phosphorus in the body, contributing to strong bones.

It is also important for supporting the immune system and preventing certain diseases.

Vitamin D exists in two main forms:

• Vitamin D2 (ergocalciferol) : derived from plants and fortified foods.
• Vitamin D3 (cholecalciferol) : produced by the skin when exposed to sunlight.

Both forms can be measured in the blood using the 25-Hydroxy test, which is commonly used to assess overall vitamin D levels.

Vitamin D testing is recommended in several situations, including when concerns about bone health or specific deficiency symptoms are present.

Common reasons include:

• Bone disorders, such as osteoporosis or rickets in children.
• Low energy levels or unexplained muscle weakness.
• Recurrent bone fractures or pain.
• Limited sun exposure, especially in winter.
• Gastrointestinal disorders that affect the absorption of nutrients, such as Crohn's disease or celiac disease.
• Monitoring levels in people taking vitamin D supplements.
• Assessment of signs of toxicity, including nausea, vomiting, or headache.

Vitamin D levels are usually measured through a blood test.

The test specifically detects 25-Hydroxy Vitamin D in the blood, reflecting the combined levels of D2 and D3.

Types of Vitamin D Tests

• Routine blood test : A simple blood test done in the laboratory to measure 25-Hydroxy levels.
• Complete metabolic panel (CMP) : Sometimes vitamin D levels are assessed as part of a larger panel that includes calcium and other markers of bone health.

Preparations for the Test

• Fasting : Refrain from eating for at least 4 hours prior to the test.
• Avoid smoking : Do not smoke for at least 30 minutes prior to the test.

Normal levels may vary slightly between laboratories, but the general guidelines are:

• Adults : 30-80 ng/mL
• Pregnant women :
  • 1st quarter : 20-65 ng/mL
  • 2nd quarter : 72-160 ng/mL
  • 3rd quarter : 60-119 ng/mL

note : The units of measurement and the normal ranges may vary between laboratories. Always consult your doctor for accurate interpretation.

High Vitamin D Levels (Hypervitaminosis D)

High levels of vitamin D in the blood, called hypervitaminosis D, are rare but can have several causes:

Common causes:

• Excess supplements : Overconsumption of vitamin D supplements can lead to dangerously high levels.
• Excessive sun exposure : Although rare, prolonged sun exposure without protection can increase vitamin D levels.
• Food sources : Excessive consumption of foods rich in vitamin D, such as fatty fish or fortified products.

Recommendations:

• Reduce or stop taking supplements in consultation with a health professional.
• Limit sun exposure, especially without protection.
• Consult a specialist if the levels are excessively high.

Low Vitamin D Levels (Vitamin D Deficiency)

Vitamin D deficiency is more common and can lead to a variety of health problems, especially related to bone health.

Common causes:

• Lack of sunlight : People living in areas with little sunlight or spending little time outside.
• Aging : With age, the skin's ability to produce vitamin D decreases.
• Insufficient food intake : A diet low in foods rich in vitamin D, such as fish, eggs, or fortified dairy products.
• Medical problems : Diseases that affect the absorption of nutrients, such as Crohn's disease or celiac disease.
• Some medications : Anticonvulsants and glucocorticoids may interfere with vitamin D metabolism.

Recommendations:

• Increase sun exposure : Spend time outside, especially in the morning or late afternoon.
• Eat foods that are rich in vitamin D : Fatty fish, egg yolks, and fortified dairy or vegetable products.
• Take supplements : In consultation with a doctor, especially if the levels are very low.
• Treat underlying conditions : Managing medical conditions can improve vitamin D levels.

In the case of abnormal vitamin D levels, it is important to consult a health professional to determine the cause and appropriate treatment.

• General practitioner : For initial screening and advice on supplement use or lifestyle changes.
• Nutritionist : To develop a dietary plan rich in vitamin D.
• Pediatrician : To manage levels in children, especially in cases of rickets or developmental concerns.
• Gastroenterologist : If a digestive condition, such as Crohn's disease or celiac disease, is the cause.
• Endocrinologist : For cases where the deficiency is linked to bone or metabolic disorders.