The royal residence added that the 95-year-old ruler Queen Elizabeth got back from the private emergency clinic in focal London at noon on Thursday and is "feeling great", the royal residence added.
The Queen had dropped a visit to Northern Ireland on Wednesday.
She was offered clinical guidance to rest for a couple of days after a bustling timetable of public commitment.
PM Boris Johnson said, "everyone sends Her Majesty our incredibly all the best".
He added he was "given to comprehend that really Her Majesty is naturally once again at her work area at Windsor at this very moment".
In an assertion on Thursday night, Buckingham Palace said: "Following clinical counsel to rest for a couple of days, the Queen went to the medical clinic on Wednesday evening for some starter examinations, getting back to Windsor Castle at noon today, and stays feeling great."
The Queen headed out via vehicle to the King Edward VII's Hospital in Marylebone, around 19 miles (32km) from Windsor, where subject matter experts saw her. Her permission is perceived not to be identified with Covid.
The short term visit was supposed to be intended for down to earth reasons, and the Queen embraced light obligations back at Windsor on Thursday evening.
Whenever the Queen first remained in a medical clinic beginning around 2013, she endured indications of gastroenteritis.
The King Edward VII's is a private medical clinic utilized by senior royals - including the Queen's better half, the late Duke of Edinburgh, who got therapy there recently.
The news on Wednesday that the Queen would need to drop an excursion to Northern Ireland was continually going to cause concern. Despite looking well overall and glad at the various occasions she has gone to over the previous week, it can't be faulted to remember that she is 95 years of age.
It is an exciting equilibrium for the castle to deliver sufficient insights regarding the Queen's wellbeing to keep people informed while keeping up with the security to which she is entitled.
Therefore, the news that she had been taken to the emergency clinic for tests was not declared until a report on the Sun paper's first page constrained the royal residence's hand.
Individuals will be concerned; however the consoling direction stays that she is "feeling great" on her return from the medical clinic and is all around ok to attempt some light obligations.
It has been a bustling time of genuine commitment for the Queen.
An authority record of the Queen's journal displayed something like 16 conventional occasions during October. There had been the most ideal designs for her to set out on the two-road trip to Northern Ireland this week.
She was envisioned facilitating a Global Investment Summit at Windsor Castle on Tuesday evening close by Mr Johnson.
In any case, on Wednesday, a Buckingham Palace representative said the ruler had "hesitantly acknowledged clinical counsel to rest for the following not many days".
He said the Queen was "disillusioned that she can presently don't visit Northern Ireland" - which would have involved a short term visit.