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Vitamin C in two units: the short answer
To convert vitamin c from mg/dL to µmol/L, multiply by 56.78. To go back from µmol/L to mg/dL, multiply by 0.01761 (or divide by 56.78). For example, 0.6 mg/dL × 56.78 = 34 µmol/L. The converter above works in both directions and shows where the result sits against typical reference ranges.
What the test measures
Plasma vitamin C (ascorbic acid) is reported in mg/dL in the US and µmol/L elsewhere. Ascorbic acid's molar mass is 176.1 g/mol, so 1 mg/dL = 56.78 µmol/L and 1 µmol/L = 0.0176 mg/dL.
Why the units differ
Research and NIH guidance describe deficiency as plasma vitamin C below about 11 µmol/L (0.2 mg/dL), so US results need converting to compare.
Where the factor comes from
The conversion factor comes from the molar mass (176.12 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 – mg/dL or µmol/L.
- mg/dL → µmol/L: multiply by 56.78.
- µmol/L → mg/dL: multiply by 0.01761.
- Round to the same number of decimals your lab uses.
Worked example in reverse: 17.0 µmol/L × 0.01761 = 0.30 mg/dL.
Vitamin C conversion chart
| mg/dL | µmol/L |
|---|---|
| 0.1 | 6 |
| 0.2 | 11 |
| 0.3 | 17 |
| 0.4 | 23 |
| 0.6 | 34 |
| 0.8 | 45 |
| 1 | 57 |
| 1.5 | 85 |
| 2 | 114 |
| µmol/L | mg/dL |
|---|---|
| 6 | 0.11 |
| 11 | 0.19 |
| 17 | 0.3 |
| 23 | 0.41 |
| 34 | 0.6 |
| 45 | 0.79 |
| 57 | 1 |
| 85 | 1.5 |
| 114 | 2.01 |
Vitamin C levels: what the numbers mean
| Category | mg/dL | µmol/L |
|---|---|---|
| Deficiency<11 µmol/L – risk of scurvy | < 0.2 | < 11 |
| Low / marginal11–23 µmol/L | 0.2 – 0.4 | 11 – 23 |
| Typical adequate rangeAbout 23–114 µmol/L | 0.4 – 2 | 23 – 114 |
Approximate cut-offs; plasma vitamin C reflects recent intake and the sample must be protected from light and processed quickly.
Approximate cut-offs; plasma vitamin C reflects recent intake and the sample must be protected from light and processed quickly.
Interpreting vitamin c results
Scurvy still occurs today, mainly in people with very restricted diets, alcohol use disorder, some eating disorders or after bariatric surgery. Early signs are fatigue, easy bruising, bleeding gums and corkscrew hairs. Smokers need more vitamin C. Because plasma levels track recent intake, a single low result after a short illness is less meaningful than persistently low results with symptoms.
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 50 µmol/L vitamin C in mg/dL?
50 × 0.0176 = 0.88 mg/dL.
Can a blood test show vitamin C deficiency reliably?
Mostly, if the sample is handled correctly. Vitamin C breaks down quickly in drawn blood, which can make results falsely low.
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.