The international unit measurement was used by the United States in 1968–2016. 1 IU is the biological equivalent of about 0.667 mg d (RRR)-alpha-tocopherol (2/3 mg exactly), or of 0.90 mg of dl-alpha-tocopherol, corresponding to the then-measured relative potency of stereoisomers. In May 2016, the measurements have been revised, such that 1 mg of "Vitamin E" is 1 mg of d-alpha-tocopherol or 2 mg of dl-alpha-tocopherol. The change was originally started in 2000, when forms of Vitamin E other than alpha-tocopherol was dropped from dietary calculations by the IOM. The UL amount disregards any conversion. The EFSA has never used an IU unit, and their measurement only considers RRR-alpha-tocopherol.