Despite Stevens' advanced skin cancer, the two marry.
Justin Chambers commented on his character's inability to tell Stevens that he loves her in the beginning of their relationship, saying that Karev has difficulty expressing himself.
Rhimes later retracted her comments and stated that she has no plans to ever re-approach Izzie's storyline again.
In the ninth season, Karev befriends intern Jo Wilson.
As the character developed, he displayed more empathy for patients and is shown to have a gift for connecting with young children, despite his repeated claims to dislike them.
Although Karev and Stevens had an on-off romantic history in previous seasons, it was not until the fifth season that the two formed a lasting relationship.
He initially makes a poor impression on his fellow interns meeting fellow interns Meredith Grey (Ellen Pompeo), Cristina Yang (Sandra Oh), George O'Malley (T. Knight), and Izzie Stevens (Katherine Heigl) whom he later taunts when he discovers she used to be a lingerie model.
After initial disagreements, Alex reveals to Izzie that his father was a heroin addict who used to beat his mother.
However, they get back together again in the fourteenth season.Introduced as a surgical intern at the fictional Seattle Grace Hospital.Karev eventually obtained the position of resident, later becoming a pediatric surgical fellow. The character is initially disliked by his fellow interns, and is often accused of being brusque and dismissive with his patients and co-workers.Alex was present when Aaron had to be committed to a psychiatric ward.
Alex secured a position in the surgical residency program at Seattle Grace Hospital after graduating from the University of Iowa.
After retaking his exams, Alex manages a pass, and reunites with Izzie after a bomb scare in the hospital.