25OHVitaminD

25-hydroxyvitamin D, also known as calcidiol, is the main circulating form of vitamin D in the blood. It is produced in the liver by the hydroxylation of vitamin D. This form of vitamin D is then transported in the bloodstream to the kidneys where it is further hydroxylated to the active form, 1,25-dihydroxyvitamin D (calcitriol), or it can be stored in adipose tissue. Measuring 25-hydroxyvitamin D levels in the blood is the standard method for assessing vitamin D status in individuals. This is because its half-life is longer than that of vitamin D itself, making it a more reliable indicator of long-term vitamin D stores. Low levels of 25-hydroxyvitamin D can indicate vitamin D deficiency, which is associated with various health issues, including rickets in children and osteomalacia in adults. Conversely, excessively high levels can lead to vitamin D toxicity. Factors influencing 25-hydroxyvitamin D levels include sun exposure, dietary intake of vitamin D and fortified foods, and the use of supplements. Certain medical conditions and medications can also affect its metabolism and blood concentration.