Conversions of IUs to mg. (milligrams)
Monday, October 15, 2012 at 11:45PM Sometimes vitamin labels use milligrams instead of International Units, IUs. Thus, people want a formula to convert them. This is not that simple because vitamin international units refer to a measure of activity while milligrams is just the weight of the material. 
Since every nutrient has different weight amounts to their IUs, plus different forms of the same vitamin can have different activity levels, you will not find a simple chart. For vitamin E, there are many different amounts for each form of E. There are at least 8, maybe up to 12 vitamin E forms. Vitamin D has at least 2 low active forms that can be measured, plus a high active hormone form, and depending on which is measured, a different IU would apply.
For vitamin A: 1 IU is the biological equivalent of 0.3 mcg retinol, or of 0.6 mcg beta-carotene
For vitamin D: 1 IU vitamin D (cholecalciferol, low active) = .025 mcg
For Vitamin E
- To convert from mg to IU: 1 mg of alpha-tocopherol is equivalent to 1.49 IU of the natural form or 2.22 IU of the synthetic form.
- To convert from IU to mg: 1 IU of alpha-tocopherol is equivalent to 0.67 mg of the natural form or 0.45 mg of the synthetic form.
1000 micrograms (mcg) = 1 milligram (mg) = .0001 gram (g)
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