The Romania international winger, 28, was tested following a training session on February 21.
The urine sample returned an adverse analytical finding for the prohibited substances stanozolol metabolites, metandienone metabolite and tamoxifen metabolite.
London-born Hihetah - who has not played this season - will see his suspension backdated from June 12 and it will run until 11 June 2023.
He joined National League 2 North club Hull from Rosslyn Park two years ago and briefly played for Yorkshire Carnegie in 2014.
Hihetah hit problems there when it emerged he was fielded as an ineligible player in a British & Irish Cup game against Aberavon at Brantingham Park.
Carnegie were docked a point in the competition table.
RFU anti-doping and illicit drugs programme manager Stephen Watkins said: “All rugby players are subject to the anti-doping rules which are in place to protect players and the integrity of our sport.”