25OH

25OH is a common abbreviation used in biochemistry and medicine to refer to 25-hydroxyvitamin D. This molecule is the primary circulating form of vitamin D in the blood and is produced in the liver from vitamin D by the enzyme 25-hydroxylase. 25-hydroxyvitamin D circulates in the bloodstream and is then converted in the kidneys to the biologically active form, 1,25-dihydroxyvitamin D, also known as calcitriol.

The measurement of 25OH levels in blood serum is the standard method for assessing a person's vitamin D status. Low levels of 25OH can indicate vitamin D deficiency, which can lead to various health problems, including rickets in children and osteomalacia in adults. Conversely, excessively high levels can also be detrimental. Factors influencing 25OH levels include sunlight exposure, dietary intake of vitamin D, and certain medical conditions or medications that affect vitamin D metabolism. Laboratories typically report 25OH levels in nanograms per milliliter (ng/mL) or nanomoles per liter (nmol/L).