Generally, the dosage of vitamin D preparation is 400IU, that is, 10 microgram, that is, 400 international units. And 1 microgram is equal to 0.00 1 mg, then 400iu vitamin d is 0.0 1 mg.

Extended data:

Vitamin D is converted from the corresponding vitamin D by ultraviolet irradiation. Provitamin D is a cyclopentane dihydrophenanthrene compound. The 5-and 7- positions in the B-ring of vitamin D are double bonds, which can absorb light quantum with wavelength of 270 ~ 300 nm, thus starting a series of complex photochemical reactions and finally forming vitamin D. If vitamin D is ergosterol, the light product is vitamin D2, and if vitamin D is 7-dehydrocholesterol, the light product is vitamin D3.

Vitamin D2, also known as ergocalciferol, is mainly synthesized by plants and contains more yeast and ergot. Vitamin D3, also known as cholecalciferol, contains 7- dehydrocholesterol in the epidermis and skin tissues of most higher animals, which can be converted into vitamin D3 by photochemical reaction under sunlight or ultraviolet radiation.

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