A board that reads: "No Guard Changing Ceremony Today" was placed in the courtyard of the palace on Thursday.
Buckingham Palace released a statement around lunchtime in England on Thursday, September 8, after the 96-year-old canceled a virtual Privy Council meeting Wednesday.
"Following further evaluation this morning, The Queen's doctors are concerned for Her Majesty's health and have recommended she remain under medical supervision. The Queen remains comfortable and at Balmoral."
While Buckingham Palace has served as the queen's main residence since her crowning in 1953, the monarch usually spends a portion of her summer at Balmoral Castle in Scotland.
The Queen's son and the heir to the throne, Prince Charles, and his wife, Camilla Duchess of Cornwall, have traveled to Balmoral to be by her side.
Prince William, who is second in line to the throne, is also en route to Balmoral.
A spokesperson told Newsweek: "The Duke and Duchess of Sussex will be traveling to Scotland."
Following the palace's statement on Thursday, Truss tweeted, "The whole country will be deeply concerned by the news from Buckingham Palace this lunchtime. My thoughts - and the thoughts of people across our United Kingdom - are with Her Majesty The Queen and her family at this time."
Truss was in the House of Commons when news broke about the royal's health. Commons Speaker Sir Lindsay Hoyle, who was handed a piece of paper updating him about the developing situation, read an official statement.
"I wish to say something about the announcement that has just been made about her majesty," he said. "I know I speak on behalf of the entire house when I say that we send our best wishes to her majesty the queen and that she and the royal family are in our thoughts and prayers at this moment."
The House of Commons had never been interrupted for news of the queen's health before.
Queen Elizabeth was born in 1926. Concerns over her health have been on the rise since the death of her husband, Prince Philip, in April 2021.