The Queen was admitted to the hospital for tests following the cancellation of her official duties.
Royal doctors got the 95-year-old to be seen by specialists in London on Wednesday afternoon.
Following her discharge, Buckingham Palace said that she was in "good spirits" following "preliminary investigations" during her hospital visit.
It is reported that her medical staff had her admitted in the hospital for precautionary reasons.
The Queen’s hospital stay comes as a first in eight years.
The Palace said: "Following medical advice to rest for a few days, the Queen attended hospital on Wednesday afternoon for some preliminary investigations, returning to Windsor Castle at lunchtime today [Thursday] and remains in good spirits."
As of recently, the Queen's health has been centre stage as she recently canceled her Northern Ireland tour as well as using a walking stick.