Kevin Rudd has been admitted to hospital for an operation to have his gall bladder removed but has promised to campaign to help Julia Gillard when he is released.

Mr Rudd's office released a statement this afternoon saying the former prime minister would be happy, upon his release, not just to campaign in his seat of Griffith but across Australia to help Ms Gillard.

Mr Rudd will have the operation later today, the statement says.

"Mr Rudd's doctors advise he is likely to be in hospital for a couple of days before returning home," it says.

"Mr Rudd looks forward to resuming campaign activities next week - both in his own electorate, elsewhere in Queensland and the rest of the country as appropriate - in support of the re-election of the government and Prime Minister Gillard."

His intention to help Ms Gillard represents a thawing of relations between the two and follows a report in today's Herald that Labor badly needed Mr Rudd to help the campaign in Queeensland, where the party's popularity is suffering.

A spokeswoman for Mr Rudd, who is running for the Brisbane seat of Griffith in the August 21 federal election, said the former Labor leader had experienced acute abdominal pain on Thursday.

He underwent a series of medical tests last night and this morning, she said.

"Based on specialist advice, he was admitted to the Mater Private Hospital around lunch time today," the spokeswoman said.

"Mr Rudd will have an operation to remove his gall bladder later today."