Browse Medical Laboratory Calculators
25-Hydroxyvitamin D (Calcidiol) Converter
25-Hydroxyvitamin D (Calcidiol) is the major circulating form of Vitamin D and the best indicator of overall Vitamin D status. It is produced in the liver from Vitamin D3 (cholecalciferol) and D2 (ergocalciferol).
While the United States typically reports results in mass units (ng/mL), most other countries use the International System (SI) molar units (nmol/L). This converter standardizes these values for accurate clinical assessment.
Mass Units (US)
StandardNanograms per milliliter (Common US Unit).
SI Units / Molar
Nanomoles per liter (International Standard).
Clinical Context
Interpretation (Endocrine Society Guidelines):
• Deficiency: < 20 ng/mL (< 50 nmol/L).
• Insufficiency: 21 – 29 ng/mL (52.5 – 72.5 nmol/L).
• Sufficiency: 30 – 100 ng/mL (75 – 250 nmol/L).
• Potential Toxicity: > 100 ng/mL (> 250 nmol/L).
Conversion Logic:
Molecular Weight of 25(OH)D: ~400.64 g/mol.
1 ng/mL ≈ 2.496 nmol/L.
1 nmol/L ≈ 0.401 ng/mL.
Clinical References
How to Use This Converter
Follow these steps to normalize 25-OH Vitamin D values.
Enter Values
Input your laboratory result into the corresponding unit field. Use ng/mL for US results or nmol/L for international.
Automatic Conversion
The calculator converts between mass units and the SI molar unit using the conversion factor of 2.496.
Reset
Use the Clear button to reset all fields.
Frequently Asked Questions
Calcidiol (25-hydroxyvitamin D) is the main form of Vitamin D stored in the body and measured in blood tests. It is different from Calcitriol (1,25-dihydroxyvitamin D), which is the active hormone.
Yes. 1 microgram per liter is numerically identical to 1 nanogram per milliliter.