Calcifediol
chemical compound
Calcifediol, also known as calcidiol, 25-hydroxycholecalciferol, or 25-hydroxyvitamin D3 (abbreviated 25(OH)D3), is a form of vitamin D produced in the liver by hydroxylation of vitamin D3 (cholecalciferol) by the enzyme vitamin D 25-hydroxylase. Calcifediol can be further hydroxylated by the enzyme 25(OH)D-1α-hydroxylase, primarily in the kidney, to form calcitriol (1,25-(OH)2D3), which is the active hormonal form of vitamin D.
Calcifediol is strongly bound in blood by the vitamin D-binding protein. Measurement of serum calcifediol is the usual test performed to determine a person's vitamin D status, to show vitamin D deficiency or sufficiency. Calcifediol is available as an oral medication in some countries to supplement vitamin D status.
Biology
Calcifediol is the precursor for calcitriol, the active form of vitamin D. It is synthesized in the liver, by hydroxylation of cholecalciferol (vitamin D3) at the 25-position. This enzymatic 25-hydroxylase reaction is mostly due to the actions of CYP2R1, present in microsomes, although other enzymes such as mitochondrial CYP27A1 can contribute. Variations in the expression and activity of CYP2R1, such as low levels in obesity, affect circulating calcifediol. Similarly, vitamin D2, ergocalciferol, can also be 25-hydroxylated to form 25-hydroxyergocalciferol, (ercalcidiol, 25(OH)D2); both forms are measured together in blood as 25(OH)D.
At a typical intake of cholecalciferol (up to 2000 IU/day), conversion to calcifediol is rapid. When large doses are given (100,000 IU), it takes 7 days to reach peak calcifediol concentrations. Calcifediol binds in the blood to vitamin D-binding protein (also known as gc-globulin) and is the main circulating vitamin D metabolite.
The public source identifies “Calcifediol” as chemical compound. This brief keeps that definition visible, then builds a research path around Calcifediol, chemical and compound.
Why this record matters
A short description can identify a subject without explaining its stakes. For “Calcifediol”, the useful work is to connect “chemical compound” to the records capable of establishing context and consequence.
Datasets, specimens, observations and peer-reviewed methods provide the appropriate test for the technical claims summarized here. The source revision retrieved here is dated Sep 28, 2025. The linked authority identifier is Q139307. None of the 0 selected statements returned an explicit reference. The first chronological checks are 2000.
A general summary may omit uncertainty, sample limits or methodological disagreement that is explicit in the technical record. The source lead contains qualifying language; that uncertainty should survive quotation, summary and reuse. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Check terminology, classification and the date of the cited evidence. Scientific names and technical consensus can change while older records retain historical value.
- Current terminology
- Classification context
- Finding cited technical literature
Primary datasets, specimen catalogues, standards bodies and the most recent peer-reviewed literature.
Three-step research path
- Establish the record: confirm the title “Calcifediol”, its source revision and the description used here.
- Expand the search: follow Calcifediol primary sources, Calcifediol archive and Calcifediol research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “Calcifediol”?
- Is the terminology current, historical or disputed?
- Has classification or technical consensus changed since the cited source?
Search terms from this dossier
This entry incorporates text from “Calcifediol” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.