87-year-old Thatcher spent Christmas in the hospital, after being operated on three days ago to remove a growth from her bladder after suffering pain earlier in the week.
Following the operation, she was said to be "in good spirits", and a spokesperson said there had been no change in her condition.
She is not expected to be released from the hospital for a few days.
The veteran ex-premier's public appearances have been very restricted over recent years due to continued ill health.