Blood Test for Vitamin D

Nonibala Ningthoujam *

Venipuncture using a vacutainer. Photo taken by Every1blowz, July 14, 2005. :: Pix - Wikipedia/Mad Max

Vitamin D is a family of compounds that is essential for the proper growth and formation of teeth and bones. The vitamin D test measures the level of vitamin D in the blood.

Vitamin D comes from two sources: endogenous, which is produced in the skin on exposure to sunlight, and exogenous, which is ingested in foods and supplements. The chemical structures of the types of vitamin D are slightly different, and they are named vitamin D2 (ergocalciferol, which comes from plants) and vitamin D3 (cholecalciferol, which comes from animals). The D2 form is found in fortified foods and in most vitamin preparations and supplements. Vitamin D3 is the form produced in the body and is also used in some supplements.

The main role of vitamin D is to help regulate blood levels of calcium, phosphorus, and to a lesser extent, magnesium. Vitamin D is vital for the growth and health of bone; without it, bones will be soft, malformed, and unable to repair themselves normally, resulting in rickets in children and osteomalacia in adults. Vitamin D has also been shown to influence the growth and differentiation of many other tissues and to help regulate the immune system. These other functions have implicated vitamin D in other disorders, such as autoimmunity and cancer.

HOW IS THE TEST USED?

A vitamin D test is used to:
o Determine if bone weakness, bone malformation, or abnormal metabolism of calcium is occurring as a result of a deficiency or excess of vitamin D.
o Help diagnose or monitor problems with parathyroid gland functioning since PTH (parathyroid hormone) is essential for vitamin D activation.
o Screen people who are at high risk of deficiency.
o Help monitor the health status of individuals with diseases that interfere with fat absorption, such as cystic fibrosis and Crohn disease, since vitamin D is a fat-soluble vitamin and is absorbed from the intestine like a fat.
o Monitor people who have had gastric bypass surgery and may not be able to absorb vitamin D.
o Help determine the effectiveness of treatment when vitamin D, calcium, phosphorus, and/or magnesium supplementation is prescribed.

WHEN IS IT DONE?

When calcium is low and/or a person has symptoms of vitamin D deficiency, such as bone malformation in children and bone weakness, softness, or fracture in adults, vitamin D test is done to identify a possible deficiency in vitamin D.

The test may be done when an individual is known to be at risk of vitamin D deficiency. Older adults, people are homebound and/or have limited exposure to sunlight, those who are obese, who have undergone gastric bypass surgery, and/or who have fat malabsorption are at an increased risk of a vitamin D deficiency. Also included in this high-risk group are people with darker skin and breastfed infants. Vitamin D test is also done before an individual begins drug therapy for osteoporosis.

When calcium is high or a person has a disease that might produce excess amounts of vitamin D, such as sarcoidosis, this test is usually done.

HOW IS THE TEST DONE?

A blood sample is needed for this test. The blood sample is usually taken from a vein in the arm.

HOW TO PREPARE FOR THE TEST?

Usually no preparation is required.

HOW WILL THE TEST FEEL?

When the needle is inserted to draw blood, a prick or a slight stinging sensation is felt.

WHAT DOES AN ABNORMAL RESULT MEAN?

o Lower-than-normal levels can be due to a vitamin D deficiency, which can result from:
o Lack of exposure to sunlight.
o Lack of enough vitamin D in the diet.
o Liver and kidney diseases.
o Poor food absorption.
o Use of certain medicines, including phenytoin, rifampicin, etc.

HOW DO WE KNOW IF TESTING IS NEEDED?

Today, we know the prevalence of vitamin D deficiency is widespread, and for this reason, feel testing is justifiable for all people. Everyone stands to benefit from knowing what their levels are and, if not optimal, supplementing their vitamin D intake.

However, people who have or are at higher risk of the following health concerns should seriously consider getting their vitamin D levels tested:
o Family history or personal history of cancer.
o Hypertension (high blood pressure).
o Schizophrenia.
o Depression.
o Migraines.
o Epilepsy.
o Osteoarthritis.
o Autoimmune conditions (such as lupus, multiple sclerosis, rheumatoid arthritis).
o Both type 1 and type I2 diabetes.
o Fibromyalgia.
o Osteoporosis/osteopenia.

In addition, anyone who experiences symptoms of:
o Musculoskeletal pain, including joint pain and low back pain.
o Muscle weakness.
o Poor balance.
o Systemic inflammation.