The singer-songwriter announced that she would miss the concert in a message posted to Twitter earlier today, but assured fans that she is on the mend.
It is not yet known why Abi is in hospital but she told fans that she hopes to be back on the stage "as soon as possible".
Abi tweeted: "Unfortunately I will not be taking part in tonight's show in Glasgow as I am in hospital.
"But not to fear as I am on the mend and hopefully will be back to it as soon as possible. I'm sure my fellow contestants will put on an excellent show x."
Reveal has contacted her rep for comment.
Abi is taking part in the show's UK and Ireland tour alongside Sam Bailey, Hannah Barrett, Luke Friend, Rough Copy, Sam Callahan and Tamera Foster.
Unfortunately I will not be taking part in tonight's show in Glasgow as I am in hospital (!) But not to fear as I am on the mend (cont)— Abi Alton (@abialton) February 28, 2014
The tour kicked off on 15 February in Belfast where the group performed some of their favourite songs from the show. It will wrap up on 29 March for their final performance in Birmingham.
On last year's X Factor, Abi left the show in week five after finding herself in the bottom two with Hannah.
At the time of her exit, she said on Xtra Factor: "I really struggled with my confidence and in my performances and Nicole [Scherzinger] has helped with that.
And hopefully will be back to it as soon as possible. I'm sure my fellow contestants will put on an excellent show x— Abi Alton (@abialton) February 28, 2014
"She takes time when she probably doesn't have it to sit me down and give me advice. I'm so thankful to her for believing in me and bringing me this far."
Despite being visibly upset after finding out she would be leaving the competition, Abi later took to Twitter to thank her fans.
"And, as one door closes another one opens," she wrote. Thank you for supporting me on this incredible journey."
We hope you get better soon, Abi.
Watch Abi sing Ed Sheeran's 'Lego House' during her time on The X Factor in the video below: