Portwood's liberation is not considered an "early release," according to the Indiana Department of Correction's chief communications officer, Douglas Garrison.
"She earned a combination of earned credit time for good behavior and completion of programming, which resulted in her period of incarceration being reduced," Garrison said.
The 23-year-old was arrested in December 2011 on drug-related charges. On Monday, Portwood was photographed leaving Rockville Correctional Facility in Rockville, Ind., wearing a white t-shirt printed with the words "Breaking Free From Addiction."
During Portwood's time on MTV's reality show, from 2010 through 2012, she had several encounters with the law. In November 2010 she was charged with domestic violence toward on-again, off-again boyfriend Gary Shirley. Later, after a June 2011 suicide attempt, she completed a rehab stint at Seasons Recovery Center in Malibu, Calif.
As part of Portwood's parole deal, the reality star will be "subject to random drug screening" Garrison said.
Portwood's brother Shawn took to Twitter to show support for his sister.
"Will be heading up to Indiana in a few days to see my sister. Can't wait until she gets out and proves she is a changed woman," he wrote.