He will be eligible to return to the Jets' active roster on Monday, Oct. 28.
Shepard told NFL.com he knowingly took the banned substances while he was recovering from shoulder and groin injuries this summer. He said sports hernia surgery he underwent led to a herniated disk in his back and he took the substances to speed his recovery, wanting to impress new coach Adam Gase.
"All that was going on, I was coming off of a subpar season and a new coaching staff, new playbook, new everything," Shepherd told NFL.com. "In my mindset, I didn't feel very confident with how everything had gone thus far. In my mind, I was so prepared to come into this offseason and have a successful offseason and train very hard. I felt that because of these limitations, I wasn't going to be able to do that. I made a rash decision, an unwise decision and a selfish decision to look to certain PEDs in order to help me with that recovery process so I would be ready to go."
He told NFL.com he thanks the Jets for allowing him to compete for a roster spot despite the looming suspension.
Shepherd, 26, was a third-round pick by the Jets last year and played all 16 games in his rookie season, with five starts. He finished with 15 tackles. He was inactive for the Jets' Week 1 game against the Buffalo Bills.
The Jets anticipated a suspension for Shepherd, which is why they kept nine defensive linemen on their opening day roster.