Liam Hemsworth has been forced to skip both the Grammys and the premiere of his new film after being hospitalised.

But fortunately for the Australian actor his new wife Miley Cyrus stepped in to represent him on the red carpet, sending him a cheeky message via Instagram.

Hemsworth's Isn't It Romantic co-star Rebel Wilson first confirmed to US TV show Extra that he had pulled out of promotional appearances.

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My love ❤️

A post shared by Liam Hemsworth (@liamhemsworth) on

"He texted us this morning. He was in hospital overnight, so hopefully he will be fine," Wilson said.

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A source told US Weekly the Hunger Games star had "cancelled his junket interviews Sunday because he was suffering from kidney stones".

Hemsworth had also been expected to be by his new wife's side at the Grammys, but Cyrus instead attended with her parents, Tish Cyrus and Billy Ray Cyrus.

Cyrus also stepped in for Hemsworth at his Isn't It Romantic premiere the next day, sending a message to her husband on Instagram.

"Getting sick blows. But so do I. Get well soon babe. I love you. Play that sax you sexy f**k," Cyrus captioned a photo of herself on the red carpet as she stood in front of a billboard of Hemsworth playing the saxophone.

In December, Hemsworth and Cyrus tied the knot in a small ceremony at their home in Tennessee surrounded by family and friends.

An insider close to the singer told People the marriage was brought on by the loss of their Malibu home during the California wildfires last year.

"They don't have doubts about their relationship," the source said. "They both wanted to get married. They have both matured a lot, and it seemed like the perfect time for them to get married."

Hemsworth and Cyrus have dated since 2009, after meeting while filming romantic drama The Last Song.

Last week, Hemsworth revealed his wife's name was now "Miley Ray Hemsworth," but she would still go by Miley Cyrus professionally.

"I think that was honestly one of the best things about it. I didn't ask her to take my name, but then she's like, 'No, of course I'm taking your name,'" he told Live with Kelly & Ryan in the US.

"I'm like, 'That's awesome. That's really good.'"