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Vitamin A in two units: the short answer
To convert vitamin a from µg/dL to µmol/L, multiply by 0.0349. To go back from µmol/L to µg/dL, multiply by 28.65 (or divide by 0.0349). For example, 50 µg/dL × 0.0349 = 1.75 µmol/L. The converter above works in both directions and shows where the result sits against typical reference ranges.
What the test measures
Serum retinol is the usual blood test for vitamin A. US labs report it in µg/dL; SI labs and WHO use µmol/L. Retinol's molar mass is 286.5 g/mol, so 1 µg/dL = 0.0349 µmol/L and 1 µmol/L = 28.6 µg/dL.
Why the units differ
WHO defines vitamin A deficiency at the population level as serum retinol below 0.70 µmol/L (20 µg/dL), so US results need converting to use that threshold.
Where the factor comes from
The conversion factor comes from the molar mass (286.45 g/mol) and the volume units on each side. Laboratories may round the factor slightly differently, which can change the last digit but never the clinical meaning.
How to convert step by step
- Check the unit printed next to the result on your report – µg/dL or µmol/L.
- µg/dL → µmol/L: multiply by 0.0349.
- µmol/L → µg/dL: multiply by 28.65.
- Round to the same number of decimals your lab uses.
Worked example in reverse: 1.05 µmol/L × 28.65 = 30.1 µg/dL.
Vitamin A conversion chart
| µg/dL | µmol/L |
|---|---|
| 10 | 0.35 |
| 20 | 0.7 |
| 30 | 1.05 |
| 40 | 1.4 |
| 50 | 1.75 |
| 60 | 2.09 |
| 80 | 2.79 |
| 100 | 3.49 |
| µmol/L | µg/dL |
|---|---|
| 0.35 | 10 |
| 0.7 | 20.1 |
| 1.05 | 30.1 |
| 1.4 | 40.1 |
| 1.75 | 50.1 |
| 2.09 | 59.9 |
| 2.79 | 79.9 |
| 3.49 | 100 |
Vitamin A levels: what the numbers mean
| Category | µg/dL | µmol/L |
|---|---|---|
| Severe deficiency<0.35 µmol/L | < 10 | < 0.35 |
| Deficiency (WHO cut-off)0.35–0.70 µmol/L | 10 – 20 | 0.35 – 0.7 |
| Typical adult rangeAbout 1.05–2.8 µmol/L; varies by lab | 30 – 80 | 1.05 – 2.79 |
Deficiency cut-offs from WHO; typical ranges vary by lab. Retinol falls during infection and inflammation.
Deficiency cut-offs from WHO; typical ranges vary by lab. Retinol falls during infection and inflammation.
Interpreting vitamin a results
The liver stores most vitamin A and releases it bound to retinol-binding protein, so blood levels only fall once stores are low. Infection and inflammation lower retinol temporarily, which can make someone look deficient when they are not. Deficiency causes night blindness and dry eyes and remains a major public-health issue in some low-income countries; in high-income settings it is seen mainly with fat malabsorption, after bariatric surgery or with liver disease.
A single result outside the reference range is common and often not significant on its own. Reference ranges are set so that about 1 in 20 healthy people fall outside them, and every laboratory sets its own limits for its method. Use the range printed on your report and discuss results with the clinician who ordered the test.
When to see a doctor
Contact your clinician if a result is flagged as abnormal and you have symptoms, if a value is far outside the range, or if results are changing over time. This page explains units; it cannot diagnose or replace medical advice.
Frequently asked questions
What is 0.7 µmol/L retinol in µg/dL?
0.7 × 28.6 = 20 µg/dL, the WHO deficiency cut-off.
Can vitamin A blood tests show toxicity?
Serum retinol is tightly regulated and often stays normal until liver stores are very high, so it is a poor test for excess intake.
Can I use this converter for any lab?
Yes for the unit conversion, which is fixed by chemistry. Reference ranges differ between labs and methods, so compare your converted value with your own lab's range.