The 35-year-old tweeted early last week: “Still so poorly problem getting worse no meds are helping such s*** times :(“, before revealing that she was in hospital.
The former glamour model then told followers and fans that she had to have an MRI scan.
She wrote: “Here we go drip and MRI scan for 45 mins… hate needled booo hoooo.”
Katie posted the nearly nude selfie yesterday, along with the caption: “Being ill has defo made me lose weight.”
Although she was flooded with messages of support after revealing her weight loss, some criticised her for being nearly naked in the shot.
Despite her illness, Katie is reportedly lined up to take part in the new series of Celebrity Big Brother.
A show insider said: “It might surprise people that a star as big as Katie would consider Celeb BB. But it seems she’s keen and it would be a great coup for Channel 5. It could happen this time.
“Katie’s a colourful character, opinionated and still one of the most recognisable faces in the land. She’d be a massive hit.”
It is reported that Katie will sign a massive six-figure deal to appear on the show, which kicks off next week.
Other stars said to be taking part include Sam Faiers, Dappy and Ollie Locke.