King Carl Gustaf reaches the official Swedish retirement age of 65 on Saturday but says he has no plans to slow down, DPA reported.
He became king in 1973 at the age of 27, succeeding his grandfather Gustaf VI, taking the motto "For Sweden - with the times."
In an interview with the Swedish news agency on Thursday, the king said he was very shy when he became monarch and has been "shy all my life," but was less so now.
At the end of 2010, the publication of an unauthorized biography, Carl XVI Gustaf - The Unwilling Monarch, provided tabloids with ample material about the king and his close circle of friends.
The book alleged that the king risked his security by attending private parties at sleazy night clubs and also that he had an affair with a former pop star.
Asked about the publication, the king said it "is never fun to be depicted in such a manner, and many others with me."
The king was set to meet the public Saturday at the Royal Palace, but no major events were scheduled for his birthday.