Prince Charles and Prince William are reportedly traveling to Balmoral in Scotland to be with The Queen following concerns from Her Majesty's doctors.
On Thursday afternoon, Buckingham Palace released the following statement: "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."
Following the news, the BBC has reported that her son, Prince Charles, is currently with her and that her grandson, the Duke of Cambridge "is on his way".
BBC News adds that the Duchess of Cornwall has also traveled to Balmoral.
On Tuesday, Her Majesty appointed Liz Truss as the United Kingdom's new prime minister after the latter won the summer Conservative leadership bid.
The occasion took place at Balmoral, as the Queen did not travel to London for the event, which has often taken place at Buckingham Palace for previous prime ministers.
In response to today's news, the new PM tweeted that the country should be "deeply concerned" about the Queen's wellbeing.
"The whole country will be deeply concerned by the news from Buckingham Palace this lunchtime," Truss tweeted. "My thoughts - and the thoughts of people across our United Kingdom - are with Her Majesty The Queen and her family at this time."
Additionally, Labour leader Sir Keir Starmer also shared his concerns about the news, tweeting: "Along with the rest of the country, I am deeply worried by the news from Buckingham Palace this afternoon.
"My thoughts are with Her Majesty The Queen and her family at this time, and I join everyone across the United Kingdom in hoping for her recovery."
Back in June, Queen Elizabeth II celebrated her Platinum Jubilee, with the entire nation enjoying a long weekend of celebrations to mark Her Majesty's 70-year record reign.