Conversion Math for Vitamin A, Vitamin D, and Vitamin E

There are four essential fat soluble vitamins that dogs need: Vitamin A, Vitamin D, Vitamin E, and Vitamin K.

Of these, vitamins A, D, and E aren’t expressed consistently in mg as vitamin K is. Instead, these vitamins are expressed in various units of measurement with IU, mcg, and mg being the most common.

The precise measure of one IU differs from vitamin to vitamin.

Glossary

• IU, International Unit
• RE, Retinol Equivalent
• RA, Retinol Activity
• RAE, Retinol Activity Equivalent
• mcg, Microgram
• mg, Milligram
• g, Gram

The Math

The answers provided in the below equations for vitamin A have been rounded up for your label comparison ease.

Vitamin A: Because we feed dogs their vitamin A primarily from animal sources, we are feeding them preformed vitamin A which is retinol and is the most biologically active form.

Vitamin A: 1 IU is the biological equivalent of 0.3 mcg retinol, or of 0.6 mcg beta-carotene

To convert vitamin A from IU to mcgRAE: IU/3.33 = mcgRAE

Example using a 50 lbs./23 kg typical adult dog: 1750 IU/3.33 = 525 mcgRAE

To convert vitamin A from mcgRAE to IU: mcgRAE * 3.33 = IU

Example using a 50 lbs./23 kg typical adult dog: 525 mcgRAE * 3.33 = 1750 IU

The answers provided in the below equations for vitamin D have been rounded up for your label comparison ease.

Vitamin D: We feed dogs vitamin D in their diet via D3 foods (animal sourced).

Vitamin D: 1 IU is the biological equivalent of 0.025 mcg cholecalciferol (D3) or ergocalciferol (D2).

To convert vitamin D from IU to mcg: IU/40 = mcg

Example using a 50 lbs./23 kg typical adult dog: 189.2 IU/40 = 4.73 mcg

To convert vitamin D from mcg to IU: mcg * 40 =IU

Example using a 50 lbs./23 kg typical adult dog: 4.73 mcg * 40 =189.2 IU

The answer provided in the below equations for vitamin E converted from mg to IU has been rounded down for your label comparison ease.

Vitamin E: Natural form of vitamin E is d-alpha tocopherol. It is also labeled as d-alpha tocopherol acetate, or d-alpha tocopherol succinate.

Natural Vitamin E: 1 IU is the biological equivalent of 0.67 mg d-alpha-tocopherol

To convert natural vitamin E from IU to mg: IU * 0.67 = mg

Example using a 50 lbs./23 kg typical adult dog: 15.75 IU * 0.67 = 10.55 mg.

To convert natural vitamin E from mg to IU: mg * 1.5 = IU

Example using a 50 lbs./23 kg typical adult dog: 10.5 mg * 1.5 = 15.75 IU

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