The King will go to hospital next week where he will be treated for an enlarged prostate.
The 75-year-old monarch's condition is benign but his public engagements will be postponed while he recuperates after the corrective procedure in a few days, Buckingham Palace has announced.
He was keen to share the details of his diagnosis to encourage other men who may be experiencing symptoms to get checked in line with public health advice, it is understood.
The King had a series of meetings and events planned at Dumfries House in East Ayrshire on Thursday and Friday, which are now being postponed on the advice of his doctor.
In a statement, the palace said: "In common with thousands of men each year, the King has sought treatment for an enlarged prostate.
"His Majesty's condition is benign and he will attend hospital next week for a corrective procedure.
"The King's public engagements will be postponed for a short period of recuperation."
The NHS describes a benign enlarged prostate as a condition that can affect how people urinate, and is common among men aged over 50.
"It's not a cancer and it's not usually a serious threat to health," the NHS said on its website.
"Many men worry that having an enlarged prostate means they have an increased risk of developing prostate cancer. This is not the case."
But benign prostate enlargement can sometimes lead to complications, such as a urinary tract infection, chronic urinary retention, and acute urinary retention.
The NHS also said the cause of prostate enlargement is unknown, but it is believed to be linked to hormonal changes as a man gets older.
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The balance of hormones in a person's body changes as they get older and this may cause their prostate gland to grow.
The monarch acceded to the throne just 16 months ago after spending 70 years as the heir to the throne, and was crowned last May in Westminster Abbey.