Enter the IU/mL value and select the substance into the calculator to determine the equivalent concentration in ng/mL. Because IU is based on biological activity rather than mass, the conversion depends on the selected vitamin or drug.
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IU/mL to ng/mL Formula
The following formula is used to convert a concentration from IU/mL to ng/mL.
ng/mL = IU/mL × (ng per IU)
The inverse relationship is:
IU/mL = ng/mL / (ng per IU)
Variables:
- ng/mL is the concentration in nanograms per milliliter
- IU/mL is the concentration in international units per milliliter
- ng per IU is the mass equivalent of one IU for the selected substance
To calculate ng/mL, multiply the IU/mL concentration by the substance-specific number of nanograms represented by 1 IU.
What is IU/mL to ng/mL?
IU/mL expresses the biological activity of a substance per milliliter, while ng/mL expresses the actual mass of that substance per milliliter. Since an International Unit is defined differently for different vitamins, hormones, and drugs, there is no single universal IU-to-ng conversion. Instead, each substance has its own established mass equivalent for 1 IU.
For example, 1 IU of vitamin D is commonly treated as 25 ng, while 1 IU of vitamin A (retinol) is commonly treated as 300 ng. That means the same IU/mL value can correspond to very different ng/mL values depending on the substance selected.
Common IU to ng Reference Values
- Vitamin D (cholecalciferol): 1 IU ≈ 25 ng
- Vitamin A (retinol): 1 IU ≈ 300 ng
- Vitamin A (beta-carotene): 1 IU ≈ 600 ng
- Vitamin E (d-α-tocopherol): 1 IU ≈ 670,000 ng
- Vitamin E (dl-α-tocopheryl acetate): 1 IU ≈ 900,000 ng
- Penicillin G: 1 IU ≈ 600 ng
- Generic substance: 1 IU = 1 ng
How to Convert IU/mL to ng/mL?
The following steps outline how to convert IU/mL to ng/mL.
- First, determine the concentration in IU/mL.
- Next, identify the substance and its conversion factor in ng per IU.
- Multiply the IU/mL value by the ng per IU factor using the formula ng/mL = IU/mL × (ng per IU).
- After inserting the values and calculating the result, check your answer with the calculator above.
IU/mL to ng/mL Conversion Table
The table below shows example conversions for a concentration of 1 IU/mL for several common substances.
| Substance | Approx. ng per IU | 1 IU/mL in ng/mL |
|---|---|---|
| Vitamin D (cholecalciferol) | 25 | 25 ng/mL |
| Vitamin A (retinol) | 300 | 300 ng/mL |
| Vitamin A (beta-carotene) | 600 | 600 ng/mL |
| Vitamin E (d-α-tocopherol) | 670,000 | 670,000 ng/mL |
| Vitamin E (dl-α-tocopheryl acetate) | 900,000 | 900,000 ng/mL |
| Penicillin G | 600 | 600 ng/mL |
| Generic substance (1 IU = 1 ng) | 1 | 1 ng/mL |
Laboratory and supplement references may report activity as IU/mL or mass as ng/mL depending on the analyte and test method. Using the correct conversion factor for the specific substance allows you to move between these units accurately.
Example Problem:
Use the following examples to test your understanding.
Example 1: Vitamin D concentration = 2 IU/mL
Vitamin D factor = 25 ng per IU
Result: 2 × 25 = 50 ng/mL
Example 2: Vitamin A (retinol) concentration = 0.5 IU/mL
Vitamin A factor = 300 ng per IU
Result: 0.5 × 300 = 150 ng/mL