Since King Harald has had a lot of health issues in recent years, I have thought a bit about the health of the two monarchs before him, so let's therefore write about the health of one of them here, i.e. King Olav V:
Was generally healthy throughout his life.
But was operated for acute stomach ulcers in April 1970. - CP Harald was regent for several weeks, and the King did not appear on the balcony on the national day, May 17.
He went skiing until he was 82 or 83. After that, he had some problems walking but managed to still walk pretty well with his walking stick.
On May 29, 1990, some of the King's staff members discovered that the almost 87-year-old monarch was ill, and he was therefore admitted to the national hospital Rikshospitalet. There, he was diagnosed with inflammation of the pericardium.
On June 2, while he was at the hospital, he suffered a stroke, which left him severely weakened.
I have read in the digital newspaper archives that the Norwegian media criticized the court for not providing enough information on how the King was doing.
On June 21, he left the hospital and started to make a few appearances in the autumn, but CP Harald remained regent for the rest of the King's life.
On January 17, 1991, after having been upset about the outbreak of the Gulf War, the already weakened King Olav suffered a heart attack at The Royal Lodge Kongsseteren.
It was decided not to move him to a hospital and instead let him die in peace.
(The above information is taken from what I have read in various places, such as books and print newspapers, which are only available in the digital newspaper archives, which are not possible to copy links from.)