The royal has subsequently canceled her official engagements for this week, including an evening event on Friday at Christiansborg Castle for the government and the Danish members of the European Parliament.
His Royal Highness the Crown Prince and Her Royal Highness are expected to take her place.
According to the royal court, the 81-year-old has moreover been forced to cancel her planned winter holiday in Norway which she should have started on Wednesday.
The royal, who has reigned for half a century, is reportedly suffering from mild symptoms and is isolated at Fredensborg Castle until she recovers.
Queen Margrethe’s health update comes after she made a trip to London to attend the late Queen’s poignant state funeral and subsequent committal service at St George’s Chapel.
Queen Margrethe II and Crown Prince Frederik were among royals and government leaders from across the world to take part in the historic occasion. The Danish royals were spotted on the front row, directly opposite King Charles III and Queen Consort Camilla.
During the moving service, members of the British royal family reunited to honour the Queen and her impressive legacy.
Among those attending were the Queen’s children – King Charles, Princess Anne, Prince Andrew and Prince Edward – and their partners, the Queen Consort, Vice Admiral Timothy Laurence and the Countess of Wessex.
The Prince and Princess of Wales also attended, along with the Duke and Duchess of Sussex, and the Queen’s other grandchildren, Princesses Beatrice and Eugenie, Zara Tindall and Peter Phillips, and Lady Louise Windsor and James, Viscount Severn.
Following the Queen’s funeral, there was a committal service held at St George’s Chapel in Windsor. The Service was led by The Right Reverend David Conner, KCVO, Dean of Windsor.
After the prayers and hymns, the Dean of Windsor, will do a Reading of Revelation 21.1-7. Other ministers will read various prayers, including The Lord’s Prayer.