The King has been briefly hospitalised due to side effects from his cancer treatment, Buckingham Palace says – with royal sources saying it was just a “minor bump in the road”.

The 76-year-old monarch has been undergoing treatment since he was diagnosed with an unspecified form of cancer in February last year following tests after a corrective procedure for an enlarged prostate.

The palace said the King had returned home to Clarence House, and that as a precaution his engagements for Friday would be rescheduled.

The Queen did not accompany him to hospital.

“His Majesty was due to receive credentials from the ambassadors of three different nations this afternoon. Tomorrow, he was due to undertake four public engagements in Birmingham and is greatly disappointed to be missing them on this occasion,” a palace spokesperson said on Thursday (British time).

“He very much hopes that they can be rescheduled in due course and offers his deepest apologies to all those who had worked so hard to make the planned visit possible.”

The palace declined to give any details of the side effects. But a royal source described Thursday’s setback as no more than the “most minor bump in the road that’s very much heading in the right direction” and that it was not uncommon with medical treatments.

The King’s recovery continued to be very positive and he was in good form and continuing to work and make calls from his study, the source said.

The royals’ state visit to Italy next month is expected to go ahead as planned, and no other health update is anticipated.

The King’s initial cancer diagnosis came as a shock less than 18 months into his reign.

However, royal aides have been upbeat about his health since and while his diary is carefully managed, he has returned to a busy schedule of work.

With the King renowned as a workaholic who often works until late into the night on his official papers, the Queen and other family members have said he needs to be encouraged to slow down.

The royal source said his medical team was fully involved in discussions over his schedule, saying reactions to treatment could be unpredictable.

The King’s illness has coincided with that of his daughter-in-law Kate, 43, the wife of his elder son Prince William, who has also been treated for cancer.

She said in January she was in remission and has gradually been returning to duties.