Vitamin D Blood Test
From Health Facts
Latest Edit: Hector 2014-03-21 (EDT)
| See Also | Lab Tests |
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This test is conducted to determine vitamin D deficiency, to determine if vitamin D supplementation level is appropriate, or if a person is receiving vitamin D therapy.[1], [2]
Discussion
- Two forms of vitamin D can be measured in the blood; 25-hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1, 25(OH)(2)D].
- 25-hydroxyvitamin D is the major form of the hormone found in the blood and is the inactive precursor to the active hormone, 1,25-dihydroxyvitamin D.
- The sources of vitamin D include endogenous sources, produced in the skin on exposure to sunlight, and exogenous sources such as foods and supplements.
- The main role of vitamin D is to help regulate the absorption of calcium, phosphorus, and magnesium (to a lesser extent).
- Since vitamin D is a fat-soluble vitamin and is absorbed from the intestine like a fat, it is sometimes used to monitor individuals with diseases that interfere with fat absorption, such as cystic fibrosis and Crohn's disease.
Patient Preparation
- No preparation is required.
Clinical Implications
High levels indicate:
- Excess supplementation (pills or other nutritional supplements)
- Sarcoidosis
- Lymphomas
Low levels indicate:
- Inadequate exposure to sunlight
- Inadequate dietary vitamin D
- Malabsorption
- kidney disease
- Drugs that interfere with production of 25-hydroxyvitamin D in the liver, such as phenytoin (Dilantin)
Associated Tests
References
- ↑ Pagana Kathleen D, Pagana Timothy J (2006) Mosby's Manual of Diagnostic and Laboratory Tests, Mosby.
- ↑ Weatherby Dicken, Ferguson Scott (2002) Blood Chemistry and CBC Analysis: Clinical Laboratory Testing from a Functional Perspective, Bear Mountain.
