Queen Elizabeth II underwent “some preliminary investigations” on Wednesday, Buckingham Palace announced.
It came after she accepted medical advice to rest for a few days and has cancelled a trip to Northern Ireland.
The palace didn’t offer specifics but says the 95-year-old monarch is “in good spirits″ and returned home to Windsor Castle on Thursday.
They previously express she was disappointed that she will no longer be able to visit Northern Ireland for engagements that were to take place this week.
“The Queen sends her warmest good wishes to the people of Northern Ireland, and looks forward to visiting in the future,″ the palace said.
She is resting at Windsor Castle, where she has stayed since the onset of the COVID-19 pandemic last year.
The decision comes just days after Elizabeth was seen using a walking stick at a major public event when attending a Westminster Abbey service marking the centenary of the Royal British Legion, an armed forces charity.
She had previously been photographed using a cane in 2003, but that was after she underwent knee surgery.
The queen, who was widowed this year, still keeps a busy schedule of royal duties. On Tuesday, she held audiences with diplomats and hosted a reception at Windsor Castle for global business leaders.