Vitamin D converter: ng/mL to nmol/L and back
Vitamin D results come in two units. U.S. labs usually report ng/mL. Canada, the UK, Europe, and Australia usually use nmol/L. The same blood reads 30 in one and 75 in the other, so a result, a cutoff, or a supplement study quoted in the wrong unit can be off by a factor of 2.5. Enter your result in either unit.
The conversion
nmol/L = ng/mL × 2.496
ng/mL = nmol/L × 0.4006
The factor comes from the molar mass of 25-hydroxyvitamin D, 400.64 g/mol. Most people round it to 2.5 and 0.4, which is close enough for reading a result: 30 ng/mL is 74.9 nmol/L exactly, or 75 rounded.
| ng/mL | nmol/L |
|---|---|
| 10 | 25 |
| 12 | 30 |
| 20 | 50 |
| 30 | 75 |
| 40 | 100 |
| 50 | 125 |
| 60 | 150 |
| 100 | 250 |
The cutoffs below are round numbers in both units because they were written that way, not because the conversion is exact.
What the result means
The test is 25-hydroxyvitamin D, written 25(OH)D, the form that reflects your stores. Two sets of cutoffs are in common use, and they disagree between 20 and 30 ng/mL.
| ng/mL | nmol/L | Institute of Medicine (2011) |
|---|---|---|
| Below 12 | Below 30 | At risk of deficiency |
| 12 to 19 | 30 to 49 | At risk of inadequacy for some people |
| 20 to 50 | 50 to 125 | Adequate for most people |
| Above 50 | Above 125 | Possibly linked to adverse effects |
The Institute of Medicine, now the National Academy of Medicine, set 20 ng/mL (50 nmol/L) as enough for bone health in almost everyone. The Endocrine Society’s 2011 guideline instead called below 20 ng/mL deficiency and 21 to 29 insufficiency, and aimed for 30 or more. Many U.S. labs adopted 30 as the bottom of their range, which is why 24 ng/mL can be flagged low on one report and read as adequate under the other framework.
In 2024 the Endocrine Society’s updated guideline withdrew those cutoffs. It no longer endorses 30 ng/mL as a target or any level as defining sufficiency. The converter shows both readings so you can see which one your lab’s range follows.
Mixed units in your history
If you’ve moved countries or switched labs, your history may have both units. A jump from 32 to 80 is a unit change, not a change in you. Convert every result to one unit before you compare them or chart them.
Converted values won’t always match the other lab’s printout to the last digit, because labs round. Vitamin D assays also differ from one another by more than the rounding, which matters more. How to track your vitamin D over time covers assay differences, the seasonal swing, and how much a supplement typically moves the number. For other tests, the lab unit converter covers the common pairs.
Vitamin D in HealthViewer
HealthViewer is a lab results tracker that runs on your own computer. It imports vitamin D from lab report PDFs, MyChart downloads, and direct connections to your health system, files the different test names under one test, and converts results in nmol/L so they share one chart with results in ng/mL in Trends. If your clinician gave you a target, set it as a custom range in the Test Catalog.
Everything stays in an encrypted file on your computer, with no account and no cloud service. Getting Started walks through the first import.
This converter is for reading your lab report, not for deciding on a supplement dose. Ask your clinician what level they want you at.