She appeared unsteady as she stood on the steps of her Belgravia home in central London and needed support from two helpers to stay on her feet.
But the former prime minister did manage a brief wave and a smile for the waiting media before returning inside.
Lady Thatcher was admitted to the private Cromwell Hospital in west London almost a fortnight ago with an infection following a bout of flu.
She entered hospital on 20 October for tests after failing to shake off the illness, which had already forced her to miss her 85th birthday party in 10 Downing Street. Her spokesman said she had now been given the all-clear by doctors.
Prime Minister David Cameron sent his "warmest wishes" and promised to find a new date to welcome her back to No 10 to celebrate her birthday.
Medical experts said Lady Thatcher - voted the world's most influential woman in a weekend poll - was likely to have stayed at the private hospital for a "health MoT".
Yesterday, she was whisked by car out of the Cromwell Hospital for the short journey back to Belgravia.
Five years ago, the former premier was advised by doctors not to make public speeches after she suffered a number of minor strokes. However, she still makes occasional public appearances.