Hi Susan, << I was just wondering how many International Units in a mg? On the vitamin bottle Vitamin A is measured in IU and also the D3 and the Vitamin E. All the rest is in milligrams. Why?>> They are not convertable, as far as I know. Usually the fat soluble vitamins are measured in IU's (A, E, D, K) and the water soluble vitamins, and minerals, are measured by weight (B's, C, and the minerals and other phytonutrients) using the metric system (milligrams, grams, or micrograms). << Also, what is pantothenic acid and D3 (or cholecalciferol)? >> Pantothenic acid is vitamin B5, or calcium pantothenate. It is plentiful in meat, organs, nuts, and greens, is destroyed by heat. Sometimes it is suspected as a key deficiency in cases of hypoglycemia, and it plays a critical role in many nervous system functions, adrenal functioning, and glucose metabolism. Are you considering taking supplements? Love, Liza [log in to unmask] (L:iza May)