International Unit is abreviated as IU, UI, IE - depends on the language

Intenational Units is usually abbreviated as

IU in English, and

UI in Romance languages (for example Spanish unidad internacional, French unité internationale, Italian unità internazionale, Romanian unitate internațională),

IE in several Germanic languages (for example German internationale Einheit, Dutch internationale eenheid) or as other forms (for example

Russian МЕ , международная единица [mezhdunarodnaya yedinitsa],

Hungarian NE , nemzetközi egység).