Radio host was determined to head into work despite her The TV star, 45, revealed she is going to have to wear a medical boot for six weeks after suffering a stress fracture.
She alongside and completed in just over six and half hours. However, Kelly ended up in hospital after the run where she was diagnosed with a stress fracture on her foot.
The describes those fractures as "tiny cracks in the bone caused by overuse". She had been keeping fans updated on her training and admitted to her followers she was "sore but happy" to have completed the gruelling challenge.
Kelly - who previously shared that she hadn't ever ran more than 5k until March - said her injury was "quite common" for first time marathon runners.
She is not letting it stop her as she headed into her show with her medical boot. Kelly was filmed by her colleague as she hobbled along the corridor and gave an insight into how much she has been struggling.
Her producer Will quipped: "After one marathon and one particularly brittle tortilla chip, @iamkb is still going strong." Kelly shared the post to her own account and added: "I thought I'd just hop on here because I don't think the video that Will the producer took of me is a true representation of who I really am."
Will tried to do an impression of her as Kelly laughed: "This is supposed to be me. I have to lift my leg up cause I don't have the strength to put it up myself."
In her caption, Kelly gave a slice of reality as she wrote: "It's been a week."
Last week, Kelly opened up on her injury while on her radio show. She said: "I went for a post-marathon scan on my foot today. I've been following who also ran the London Marathon."

Kelly added: "She's all strapped up in a boot, someone stamped on her foot and cracked a bone." She continued: "My foot looked a bit like hers' so I sent her a picture and she said 'go get an X-ray!'
"Well, I've walked to three to be told I've got a broken foot. I was like I could have told you that at hospital number one!"
She added: "I cannot believe the ordeal! What time is it now? Four-thirty. I set off at nine o'clock this morning, I'm not joking!"
The former went on: "[Someone] wheeled me out to the road and then just off loaded me and I had to hobble across the road to another hospital who then didn't have an MRI. Oh, it's been a whole ordeal! The only thing they did wheel me to is a cashier so I could pay for it!"
She explained: "It seems that I've got a stress fracture which is quite common with first time marathon runners because we don't know what we're doing. So, I'm in a boot and it looks like I'll be in a boot for six weeks. But I've got a medal!"
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