The 37-year-old was pictured arriving at the ITV studios in London this morning, but she was feeling poorly as she sat with the team in a meeting.
At the start of today's show, panellist Andrea McLean revealed to the studio audience that Katie has food poisoning.
"You may notice that there's an empty chair," said Andrea. "Katie was supposed to be on the show but she's had a little bit of a medical emergency this morning. That woman is a trooper but she's not very well."
Mum-of-five Katie even filmed a segment for the show, as she laid across a sofa covered in a duvet.
Katie said: "I haven't been sick for about an hour now but I still feel sick, from both ends."
Still in good spirits, she joked: "Don't miss my banter too much."
A medic was also filmed in the segment, advising Katie that she should go home and rest.
After, Andrea praised Katie for her work ethic, adding: "She came in anyway and had to keep dashing in and out of the meeting."
It was then revealed that Katie's replacement will be Michelle Heaton, who was actually scheduled to appear on the show as a guest anyway.
News about Katie's illness was first announced on This Morning, as panellist Andrea revealed to hosts Ben Shepherd and Ruth Langsford: "Katie is resting up in the green room right now, so we might be down a person today."
The official Loose Women Twitter account wrote: "It's a bit touch and go whether @MissKatiePrice will make today's show.....the nurses are tending to her...."
The next tweet read: "Was that @MissKatiePrice we just saw leaving? With a prescription in her hands?"
They later added: "Get well soon @MissKatiePrice! We miss you!"
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