Queen Elizabeth has been admitted to a London hospital today as a precaution after experiencing symptoms of a stomach bug, according to a Buckingham Palace spokesperson.
The 86-year-old monarch is being assessed for symptoms of gastroenteritis at King Edward VII hospital in London.
All official engagements for this week, including the Queen's trip to Rome, will be either postponed or cancelled as a precaution, the palace said.
Queen Elizabeth is said to be in good spirits and is expected to be in the hospital for two days.
Gastroenteritis is an infection that causes inflammation of the stomach lining and intestines. Symptoms can include vomiting, fever and a stomach ache.
The queen's sickness was first announced on Friday, and she spent Saturday resting at Windsor Castle, just outside of London.
Queen Elizabeth rarely miss engagements due to illness. She was last hospitalized ten years ago when she underwent keyhole surgery on her knees.
In 2012, the monarch marked 60 years on the throne with a massive Diamond Jubilee celebration.
Kate Middleton spent several days in King Edward VII hospital in December 2012, where she was treated for acute morning sickness in the early stages of her pregnancy.
ABC News' Jean-Nicholas Fievet contributed reporting.