The princess has suffered from health complaints over a period of time, the palace confirmed in a press statement.
Palace deputy head of communication Sven Gjeruldsen declined to go into further details as to the nature of the health complaints affecting the Crown Princess, NRK writes.
But the princess is scheduled to undergo a minor operation on Monday, according to the report.
That procedure will keep her sidelined from royal duty until next month.
A trip to German city Leipzig scheduled for Saturday has been cancelled as part of the sick leave.
Crown Princess Mette-Marit received surgery in 2013 for a neck problem that had troubled her over a period of time, having been sustained in a fall during a visit to Ukraine in 2008.
In 2016, she cancelled participation in a black tie event in honour of the Polish president, also citing a back injury.