Norway's royal household said in April 2024 King Harald would make a "permanent reduction" to his public engagement "out of consideration for his age".
The king ascended the Scandinavian country's throne in January 1991 and has openly ruled out abdicating.
He was taken to hospital in February on the Spanish island of Tenerife while suffering from an infection and dehydration.
In 2024, the king was fitted with a pacemaker having fallen ill on holiday in Malaysia.
Queen Sonja was also admitted to hospital in May this year for examinations and observation due to heart problems, the palace said.
The king and queen's health problems come after a turbulent time for the Norwegian royals.
In March, Crown Princess Mette-Marit - wife of Crown Prince Haakon - told national TV that she wishes she had never met late US sex offender Jeffrey Epstein.
The crown princess had exchanged hundreds of emails with the disgraced Epstein between 2011 and 2014, and stayed in his Florida house when he was not there.
"It is incredibly important for me to take responsibility for not checking his background more carefully," she said.
Three months later in June, her son from a previous relationship, Marius Borg Høiby, was found guilty of two counts of rape and sentenced to fours in prison.
