Is fasting required for a 25-hydroxyvitamin D test?

Generally, fasting is not required for a 25-hydroxyvitamin D test.

The 25-hydroxyvitamin D test is typically used to measure the level of vitamin D in the body and is performed via blood testing. 25-hydroxyvitamin D is an intermediate product in the metabolism of vitamin D. After vitamin D is ingested, it is generally stored under the skin and can be activated by exposure to ultraviolet light. It is then converted into 25-hydroxyvitamin D in the liver, and further transformed in the kidneys into the active form, 1,25-dihydroxyvitamin D3. This final active compound helps the body absorb calcium from the intestines into the bloodstream, which is then delivered to bones or teeth. Food intake usually does not affect the accuracy of this test, allowing for a clear diagnosis of the body's 25-hydroxyvitamin D levels and enabling accurate conclusions based on the test results.

Normally, a 25-hydroxyvitamin D level between 30–60 ng/mL is considered within the normal range, and supplementation is generally not needed. If vitamin D deficiency is detected, treatment may include vitamin D drops, calcium with vitamin D softgels, or other medications as directed by a physician. Additionally, increasing outdoor activities during daylight hours to allow sun exposure can also help boost the body’s vitamin D levels.