Elizabeth remains at her Scottish home Balmoral Castle, the palace said. A palace source said immediate members had been informed.
Prince Charles and Camilla, who are staying nearby at Birkhall on the estate have travelled to Balmoral to be with the Queen.
Prince William will also travel north from Windsor to be with his father and grandmother, multiple news outlets have confirmed, The Age reported.
For most of the year, she has endured ongoing “episodic mobility issues” that are reported to have worsened over the past few weeks.
She has been taking her traditional summer break in Scotland with family and guests. She usually stays at the estate from August to October.
On Wednesday, the Queen postponed a virtual Privy Council meeting after being advised by doctors to rest.
A Buckingham Palace spokesman said of the cancelling of the meeting: “After a full day yesterday, Her Majesty has this afternoon accepted doctors’ advice to rest.
“This means that the Privy Council meeting that had been due to take place this evening will be rearranged.”
MA/PR