The king’s cancer diagnosis was announced publicly in February 2024.

King Charles III was briefly hospitalized Thursday amid ongoing medical treatment for cancer, according to Buckingham Palace.

Charles’ hospitalization was a result of “temporary side effects” he experienced after undergoing what the palace described as “scheduled and ongoing medical treatment for cancer” on Thursday morning.

After a “short period of observation” in the hospital, the 76-year-old king returned to Clarence House, his royal residence in London, according to the palace.

King Charles III is shown during a visit to an exhibition at Somerset House, on March 26, 2025, in London.

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As a result of the hospitalization, Charles’s engagements on Thursday afternoon and Friday were postponed.

“His Majesty would like to send his apologies to all those who may be inconvenienced or disappointed as a result,” the palace said in a statement Thursday evening.

Charles’s cancer diagnosis was announced by Buckingham Palace in February 2024, shortly after he underwent treatment for benign prostate enlargement.

In announcing Charles’ diagnosis, the palace did not specify the type of cancer, the stage of cancer or the type of treatment he is undergoing or planning to undergo.

King Charles III arrives for a visit to an exhibition at Somerset House, on March 26, 2025, in London.

Chris Jackson/Getty Images

After spending several weeks largely out of the public eye, Charles visited a cancer treatment center on April 30, 2024, in his first public royal engagement since his own diagnosis.

Since then, Charles has resumed a more regular schedule of public duties.

On Wednesday, he visited an exhibition at Somerset House in London and later that evening attended a reception at Buckingham Palace.