- What is it for
- How the exam is done
- What the results mean
- Decreased vitamin D values
- Increased values of vitamin D
The vitamin D test aims to check the concentration of vitamin D in the blood, as this vitamin is important for regulating the levels of calcium and phosphorus in the blood. Learn more for what vitamin D is for.
This test is usually requested by the doctor to monitor replacement therapy with vitamin D or when there are signs and symptoms related to bone decalcification, such as muscle pain and weakness, for example, being most often requested together with the calcium dosage, PTH and phosphorus in the blood. Understand how the blood phosphorus test is done.
What is it for
The vitamin D test is done mainly to diagnose vitamin D deficiency, in addition to hypervitaminosis D. However, the doctor may also order this test when there are signs and symptoms of bone decalcification, since vitamin D is one of the factors responsible for regulating the concentration of calcium and phosphorus, in addition to promoting bone mineralization.
This test is also requested to monitor replacement therapy with vitamin D and to assist in the differential diagnosis of rickets, osteoporosis and osteomalacia, which is a disease characterized by fragile and brittle bones in adults. Learn more about osteomalacia.
How the exam is done
To perform the exam, no preparation is necessary. The test is done by drawing a small amount of blood, which is sent to the laboratory for analysis.
Vitamin D is produced from a substance derived from cholesterol present in the skin, which when stimulated by the ultraviolet light of the sun, is converted into cholecalciferol, known as vitamin D. The vitamin D produced undergoes metabolism in the liver, becoming 25- hydroxyvitamin D, which in the kidneys, under the influence of parathormone, is converted to 1, 25-dihydroxyvitamin D, which corresponds to the active and stable form of vitamin D and is responsible for increasing the absorption of calcium in the intestine and, consequently, increasing the concentration of calcium in the blood.
Both forms of vitamin D are dosed, with 25-hydroxyvitamin D being most often used to identify vitamin D deficiency, while 1, 25-dihydroxyvitamin D is usually required for people with kidney disease.
What the results mean
From the results of the dosage of 25-hydroxyvitamin D, it is possible to indicate whether the person has sufficient, insufficient or deficient amounts of vitamin D. The vitamin D reference values are:
| Meaning | Reference value |
| Deficiency | Below 10 ng / mL |
| Failure | Between 10 and 30 ng / mL |
| Sufficiency | Between 30 and 60 ng / mL |
| Toxicity | Above 100 ng / mL |
Decreased vitamin D values
The decreased values of vitamin D indicate hypovitaminosis, which may be due to little exposure to the sun or little intake of foods rich in vitamin D or its precursors, such as egg, fish, cheese and mushrooms, for example. See other foods rich in vitamin D.
In addition, diseases such as fatty liver, cirrhosis, pancreatic insufficiency, inflammatory disease, rickets and osteomalacia and diseases that lead to inflammation in the intestine can lead to vitamin D deficiency or deficiency. Know the symptoms of vitamin D deficiency.
Increased values of vitamin D
Increased vitamin D values are indicative of hypervitaminosis, which can happen due to prolonged exposure to sunlight or vitamin D intoxication, for example. Learn how to sunbathe to produce enough vitamin D.
