Thatcher, 87, was admitted to hospital on Thursday for a minor operation to remove a growth in her bladder after suffering pain earlier in the week.
She is likely to remain in hospital over Christmas.
“I understand she is in good spirits,” a spokesman said.
“Given her age, I don’t think she will be coming out for a few days.”
The former Conservative Party leader was Britain’s prime minister from 1979 to 1990. She remains Britain’s only female premier.
Earlier Sunday, public relations executive Lord Tim Bell, who advised the “Iron Lady” for her 3 general election victories, said Thatcher was doing “fine.”
“She is (at the hospital) at the moment and she’s fine,” he told AFP.
He said that her daughter Carol was at her side and that he had “no idea at all” when Thatcher would leave hospital.
Bell has described the operation as “minimally invasive surgery.”
On Friday, current Conservative Prime Minister David Cameron’s office wrote on Twitter that the “PM wishes Lady Thatcher a speedy recovery.”
In recent years, Thatcher — the 20th century’s longest continuous occupant of 10 Downing Street — has cut a subdued figure.
After a series of minor strokes, she was told by doctors to quit public speaking in 2002. With dementia taking hold, she has appeared increasingly rarely in public.
Her daughter once revealed that the former premier had to be repeatedly reminded that her husband Denis had died in 2003. – Rappler.com