Food labels listing daily values and UIs are sometimes difficult for the average person to understand; and reading nutrition information labels can feel like reading a different language when things are phrased in unfamiliar terms.
Definition of UI
UI is an abbreviation of the term "International Unit". It is more commonly abbreviated as "IU", although both are acceptable. The alternate abbreviation UI is due to the word "unit" coming first in many languages when the phrase is translated, for example in French, "International Unit" is "Unité Internationale". Because America is a largely English-speaking country, you are more likely to see IU instead of UI.
IU, or UI, is used in pharmacology for vitamins, hormones, some medications, vaccines, blood products, and similar biologically active substances. The definition of IU is established by international agreement, and differs from product to product; one IU of vitamin E is not equivalent to one IU of vitamin A.
IU and Daily Values
"Daily values" are guidelines set by the FDA about how much of a substance you should consume in a day. IUs are used for vitamins because the amount required is usually too small to be listed in milligrams (mg). For example, the recommended daily IU value for vitamin D is 400, which means that you should consume at least that much vitamin D every day.