Crown Princess Mette-Marit's sick leave has been extended, the Norwegian royal palace confirmed on Thursday.
The royal, 51, was diagnosed in 2018 with pulmonary fibrosis, a chronic lung condition that causes the lung tissue to become damaged.
She was first placed on sick leave from her royal duties on 23 October after beginning a new bout of treatment.
In the latest statement, the court said: "Due to side effects of the medicines the Crown Princess must take for her chronic lung disease, the sick leave has been extended, initially until 5 November. Program items during the period will be cancelled or postponed."
Mette-Marit was last seen publicly on 21 October as she and her husband, Crown Prince Haakon, marked the 25th anniversary of the Nordic countries' joint embassy facility in Berlin.
The Crown Princess's extended sick leave comes amid the scandal involving her son, Marius Borg Høiby, who is the stepson of Haakon.
The 27-year-old admitted to assaulting his 'girlfriend' following his arrest in August.
The Norwegian news outlet Se og Hør reported that Marius was also involved in a burglary at Mette-Marit and Haakon's residence, Skaugum, after he threw a "wild party" and no longer has access to the property.
Police also confirmed to Aftenposten on Thursday that Mette-Marit's son has lost his driving licence, but it's not clear when this was revoked.
The Crown Prince and Crown Princess are also parents to Princess Ingrid Alexandra, 20, and Prince Sverre Magnus, 18.
Haakon's father, King Harald V, 87, appeared to allude to the Norwegian royal family's difficult year in a speech at the Storting (Norwegian Parliament) last week.
The monarch, who has reigned since 1991, was hospitalised during a private holiday in Malaysia in February and was later fitted with a pacemaker after being flown home to Oslo.
In his address, King Harald said: "The royal family is a team that works well together. And then we are a family - with the joys and challenges that we all know can come with it. In both good and difficult times, we try to stand together and support each other.
"We are grateful for all the warmth and consideration that has been shown to us throughout this special and demanding year - right from when I had to be flown home in February on sick leave.
"Sometimes life is simply very difficult. It's something everyone can experience - including our family.
"When people we are happy with are not well, it hurts those around them. We try our best to take care of each other. Tonight we send an extra warm thought to everyone who is in pain."