Prince Philip has suffered a number of ailments over the years, with major operations including surgery for blocked coronary artery at Papworth Hospital in Cambridgeshire in December 2011.
One reporter from British channel ITV tweeted that the Duke of Edinburgh "walked" into hospital, relieving conserved fans of the monarch's husband who were concerned over the news.
The Duke of Edinburgh is expected to spend the run-up to Christmas being cared for by medical staff, after he was admitted to hospital for treatment relating to a "pre-existing condition". Buckingham Palace has been keen to play down fears about the Duke's health and has said it was a pre-planned measure and not an emergency matter.
Queen Elizabeth arrived in Norfolk on Friday ready for Christmas celebrations at Sandringham Estate.
In 2017 he spent two nights in the King Edward VII hospital and was hospitalized for 10 days in 2018 for a hip replacement.
In a statement to BBC, the palace said it was "on the advice of His Royal Highness' Doctor". No reports on if he will miss Christmas with his family.
Prince Philip has rarely been seen in the public eye since his retirement from royal duties in 2017.
It's been a busy week for Her Majesty as she hosted a party to thank household staff on Monday, followed by a Christmas lunch with extended members of her family at Buckingham Palace on Wednesday.
The Palace confirmed Prince Philip, 98, had been residing at the Royal Family's Sandringham estate, and left on Friday morning without Her Majesty.
Philip, outspoken, irascible and intensely private and with a reputation for brusque comments and occasional gaffes, has needed hospital treatment several times in recent years.
In January this year, Philip was involved in a vehicle crash when the Land Rover Freelander he was driving flipped over after colliding with another auto near the Sandringham estate.