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Vitamin D 25-Hydroxy (Calcidiol) Blood Test Popular

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About Our Vitamin D 25-Hydroxy (Calcidiol) Blood Test

Note: Fasting is not required for this test.

This test measures Vitamin D 25-Hydroxy (Calcidiol) levels in the blood for deficiencies. The major function of vitamin D in humans is maintenance of calcium homeostasis. Individuals who are interested in vitamin D testing related to hypocalcemia and/or monitoring renal osteodystrophy or chronic renal (kidney) failure should order our Vitamin D 25-Dihydroxy (Calcitriol) Test, not this test.

Vitamin D is absorbed through both sunlight and via foods and drinks that are ingested that contain it. This fat-soluble vitamin plays a major growth and development of bones and teeth. Typically, Vitamin D's most common subcategories are Vitamin D2 and D3; Vitamin D2 comes from digesting vitamin D from plant and fungal food sources, and vitamin D3 is absorbed via the skin when it takes in sunlight.

Vitamin D is converted in the kidneys to its active form and helps to control the body's calcium and phosphate levels. It plays an important role in the growth and health of bones and teeth. When levels of vitamin D are too low, it can lead to a drop in calcium levels (hypocalcemia). Symptoms of a vitamin D deficiency include weakness, frequent infections, fatigue, aching and pain.

Malnutrition or conditions that can cause an individual to have poor absorption of nutrients like celiac disease, Crohn's disease, alcoholism or intestinal or gastrointestinal disorders may lead to low levels of vitamin D.


The Vitamin D, 25-Hydroxy (Calcidiol) Test is used to help diagnose or monitor the following conditions:

  • Rickets (a disease in children in which bone tissue fails to properly mineralize)
  • Osteomalacia
  • Hypocalcemia

Few natural foods contain vitamin D; major sources of it include:

  • Sunlight exposure/UV exposure
  • The flesh of fatty fish like tuna and mackerel
  • Fish liver oils
  • Fortified vitamin D milk
  • Some foods like egg yolks, cheese and beef liver contain small amounts of vitamin D
  • Mushrooms (not as major of a vitamin D source as the above sources, but mushrooms are a good option for vegans or vegetarians)

Overall, a Vitamin D deficiency can be more prevalent in people who are:

  • Allergic to milk
  • Lactose intolerant
  • Ovo-vegetarians
  • Vegans
  • Older adults
  • Gastrointestinal surgery patients
  • Dark-skinned
  • Living with digestive disorders like Crohn's disease or celiac disease
  • African-American infants and children (more common in the winter-time)
  • Prolonged, exclusively breastfed infants
  • Individuals who avoid being outside or wear sunscreen extensively

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