"I love you and it's been wonderful." Kyle tells Jackie O about his secret 'health condition'.

Kyle Sandilands has explained he has been living with a health condition in secret, leaving his long-time radio co-host and friend Jackie ‘O’ Henderson visibly shaken.

In a preview for a 60 Minutes interview to be aired on Sunday night, Sandilands, 48, was teary-eyed when he looked at Henderson and told her he’d been hiding a medical condition for some time.

“I love you and it’s been wonderful,” he said.

The 60 Minutes preview shows an emotional Kyle and Jackie O. Post continues below video.

The preview then cuts to interviewer Karl Stefanovic pointing out that Sandilands is crying.

"Why?" Henderson asked.

"There's a condition that I've been diagnosed with that I haven't spoken to anyone about," Sandilands said, with the camera then showing Henderson wipe tears from her eyes.

The preview ends there, so it remains unclear what exactly he is talking about.

It appears other parts of the interview will reflect on how the pair got to the top of the radio world and how hard it is to maintain that number one spot.

"I'm always worried you're going to say something and it'll just ruin you," Henderson told Sandilands.

She admitted "staying at number one is harder than getting to number one".

Typically, Sandilands responded to say he "doesn't give a f**k".

"Millions of dollars of marketing has been spent on me being a bastard," he laughed, describing Henderson as the "yin to my yang".

Henderson and Sandilands began working together on the Hot30 in 2000. They later worked on 2Day FM before moving to KIIS from January 2014, where they remain today with the number one FM breakfast show in Sydney.

Sandilands has spoken about health concerns in the past, and in October 2019 said he'd given up alcohol and drugs and started eating healthier after advice from his doctors.

"I was like a teenage boy my entire life, and that caught up with me... so that had to get sorted out," he told the Daily Telegraph.

"I've still got high blood pressure and I'm still on medication like a mess."

In September 2018, Sandilands' then-partner, Imogen Anthony, told media the reason the radio host hadn't been at work was that he was "extremely sick".

"I felt really dizzy on Wednesday morning in the shower," Sandilands told his co-host Jackie O when he returned after three days off work. "I got out of the shower, nearly slid over on Imogen’s f**king tan (lotion) that was on the ground. I sat down for 20 minutes and it was getting worse. There was no way I could drive, I was too unsteady. Then I got worse and worse."

"I was a bit sick last year, just from being [overweight] and not getting enough sleep," he told NewsCorp’s Sunday Confidential in February 2019.

"I thought, 'I can't do this, I've got responsibilities'. So I’ve lost a bit of weight. Imogen has gone hardcore so the Coca-Cola is finished, I'm on the green juice. We installed a gym over Christmas so I work out every day, just lightly. She also has me on Youfoodz."

Sandilands previously said he was drinking Coca-Cola "like it was water".

He and Anthony announced their breakup in November 2019 after eight years together.

"We haven't been living together for a few months, quite a few months, unfortunately, it’s run its course," he said on The Kyle and Jackie O Show at the time.

Imogen also announced the news on Instagram, sharing: "We have a lot to deal with separately... it's been one of the hardest years of our lives, separately. I've got so much family stuff, and you know, there's so much health stuff involved between us, and there's... we just kind of want to... get ourselves into the best form of ourselves that we can be, without kind of pissing in each other's pockets."

Now Kyle is dating Tegan Kynaston, the communications director of Kyle's company, King Kyle. She was previously his personal assistant.

The full 60 Minutes interview will air this Sunday at 8.40pm on Nine.