As announced last month, the 39-year-old will appear in three episodes of the BBC medical drama, portraying the role of brassy Barbara Alcock.
Barbara is a mature medical student and single mother, who previously worked as a physiotherapist. Her storyline sees her learning from established regular Elliot Hope (Paul Bradley).
Speaking on This Morning today (June 18), Osho explained that she made sure to do research before she started filming.
Osho commented: "I just wanted to get it all right. I started off talking to my mum because she's a nurse. She said, 'One thing is they don't get the crash trolley out nearly as much as they do in Holby!' So that was nice to hear!
"Then I found out what a physiotherapist would know already, then what sort of training they'd have to do to become a doctor. I even did an exam online! There's an introductory exam that you have to do, when you want to convert your course."
Asked how she did on the test, she joked: "I'm qualified - I'm actually a doctor!"
Pictured: Paul Bradley and Andi Osho on This Morning.
Osho appeared on the ITV1 magazine show alongside Paul Bradley, who reflected on his time in the role of Elliot.
He said: "I've been on it seven years and it feels like seven minutes, because you get different challenges every week. The character is nice - it's nice for me playing a high-stakes character."
Holby City continues tomorrow (June 19) at the unusual time of 7.30pm on BBC One.