Officials confirmed the suspension with ESPN.com on Thursday, following an initial report by MMAjunkie.com.
Rothwell (33-9) defeated Vera via TKO on Aug. 31, at the Bradley Center in Milwaukee. He had been approved a therapeutic use exemption for testosterone by the Wisconsin Department of Safety and Professional Services, but tested outside the acceptable limit after the bout.
The Wisconsin commission issued Rothwell an "administrative warning," according to a statement released to ESPN.com by his management. The UFC then elected to issue a nine-month suspension of its own.
"While the WDSPS has elected not to impose any discipline on Rothwell, to date, the UFC holds its athletes to a high standard of personal and professional conduct and finds that Rothwell's actions merit the suspension," an official UFC statement read.
The UFC went on to say Rothwell, 31, must submit a negative drug test at the conclusion of his suspension. Additionally, the win will remain intact due to the WDSPS stance. Under another commission, it would likely change to a no-contest.
This was the first time Rothwell had received a therapeutic use exemption for testosterone. He stated doctors have diagnosed him with hypogonadism, a condition possibly linked to a car accident he survived in 1999.
"This came as a shock because I had applied for and was granted a (testosterone replacement therapy) exemption and was doing so under the supervision of a doctor," Rothwell said in a released statement. "I was tested every week for eight weeks prior to the fight and was well under the acceptable level each time.
"I am not going to fight the suspension, as I feel ultimately it was my responsibility to make sure I stay under the acceptable limit. I am deeply sorry for this mistake and apologize to my fans, family and friends."