The 96-year-old monarch has been suffering from health problems since last October, which make it difficult for her to walk and stand.
“After reassessing the Queen’s health this morning, her doctors are concerned for Her Majesty’s health and recommend that she continue to be under medical care,” Buckingham Palace said in a statement.
“The Queen continues to enjoy a comfortable stay at Balmoral,” her estate in the Scottish Highlands, the palace added.
The Palace’s statement about the Queen’s health is highly unusual.
“The palace doesn’t release news about the Queen’s health unless it’s very important,” royal commentator and writer Robert Hardman told the BBC.
The Queen’s relatives are reported to be with or visiting Scotland on Thursday: son Prince Charles, 73, Princess Anne, 72, Prince Andrew, 62, Prince Edward, 58, and grandson Prince William.
Prince Harry and his wife Meghan will also travel to Scotland to see the Queen, a spokesman for the couple said on Thursday.
The couple, who are currently on a short tour of Europe, were due to attend an awards ceremony in London on Thursday night, but changed their plans and are coming to meet the Queen, Britain’s Press Association news agency reported.
“The whole country is very concerned”
The latest announcement about the Queen’s health came a day after the Queen canceled a meeting of her Privy Council and was told to rest.
On Tuesday, at her summer residence in Scotland, Balmoral Palace, she accepted Prime Minister Boris Johnson’s resignation and met with Liz Truss, whom she asked to form a new government.
The new Prime Minister of the United Kingdom, for her part, wrote on Twitter that the whole country is concerned about the Queen’s health.
“The whole country is deeply concerned by the news that reached us this lunchtime from Buckingham Palace,” Truss tweeted after the royal palace’s statement.
“My thoughts – and the thoughts of all the people of the United Kingdom – are with Her Majesty the Queen and her family at this time,” she added.
This year, Elizabeth II celebrated the 70th anniversary of her reign. In recent months, she has increasingly handed over duties to her heir, Prince Charles, and other members of the royal family.
The Queen admitted that she felt “exhausted” after contracting COVID-19 earlier this year. On the rare occasions when she appeared in public, she walked with the aid of a cane.
After the Chelsea Flower Show in London, Elizabeth II drove around in a golf cart.
In early June, she made two public appearances during four days of celebrations to mark the 70th anniversary of her coronation.
But even then she was forced to miss a service marking the anniversary of her reign and a concert by pop stars outside Buckingham Palace.
However, the Queen appeared on the balcony together with her direct heirs – Prince Charles, his son William and grandson George.
The monarch traveled to Balmoral following reports that a lift had been installed near the stairs at her private estate.