Baroness Thatcher has left hospital after being admitted for tests.
Baroness Thatcher told waiting reporters that she was feeling better
The 82-year-old former UK prime minister spent the night at St Thomas' Hospital in London after falling ill at a House of Lords dinner.
Her spokesman said she felt "giddy and queasy". However, she waved to photographers as she walked to a waiting car as she left hospital.
In 2002, Lady Thatcher had a series of minor strokes and was advised by doctors to stop making public speeches.
A spokesman for Lady Thatcher said they thought it best to take her to hospital for tests after her "legs buckled" at the end of the function.
He told the BBC she had a "comfortable night" in hospital and all tests seem "quite clear".
Her daughter, Carol, said the decision to take her mother to the nearby hospital was a wise one given her medical history.
"But it's good news today. She is doing well."
Prime Minister Gordon Brown said: "I and others wish her well in a very speedy recovery".
Charles Moore, former editor of the Daily Telegraph and a biographer of Lady Thatcher, said people close to her were "optimistic" about her condition.
He told BBC News: "Things are not too bad."
Baroness Thatcher met Chelsea pensioners last month
He added: "I've just spoken to some people close to her and I think what seems to have happened, Lady Thatcher is susceptible to heat and it sometimes gives her - and it does sometimes with old people - a turn.
"I think that's what's happened but obviously there is always some concern with someone that age."
The Tory peer's strokes have affected her short-term memory, according to friends, but she continues to fulfil a number of public engagements.
She last appeared in public three weeks ago when she opened a new infirmary for Chelsea pensioners.
In January, Lady Thatcher was presented with a lifetime achievement award by David Cameron at a ceremony in London.
The current Conservative leader described her as a "towering figure" who had "transformed our country".
She also won praise from Prime Minister Gordon Brown during a high-profile visit to Downing Street last year. Labour's long-time foe was, he said, a "conviction politician".
It was a visit that led Tory MPs to accuse Mr Brown of hypocrisy.
Lady Thatcher lives in Belgravia, central London. Her husband, Sir Denis Thatcher, died in June 2003, aged 88.
She was prime minister for 11 years before resigning, under pressure from her party, in 1990.