Toronto Mayor Rob Ford has been discharged from hospital, where he has received care for a throat infection that has aggravated his asthma.

The mayor left Humber River Regional Hospital Thursday afternoon "in good spirits, good health and ready to get back to [city hall], said Isaac Ransom, a spokesman for the mayor's office in a tweet.

Mayor Rob Ford's press secretary, George Christopoulos, released this photo of Ford 'taking care of business' in hospital. (Twitter)

Coun. Doug Ford, the mayor's brother, told reporters earlier that his brother was doing fine.

"Rob's healthy as a horse," said the councillor. "He's a workaholic. He'd outwork probably 99 per cent of the population out there, and sometimes you go overboard. You're working day in and day out. You get burnt out."

The mayor's press secretary, George Christopoulos, on Wednesday tweeted a photo of the mayor examining a report. The caption was "#Toronto Mayor Rob Ford taking care of business."

Doug Ford said the mayor may have to make a few personal changes.

"I'm sure the doctors beat him down on his weight," said Ford.

"Rob has to focus on losing a few pounds, but what Rob has going for him is his age. As the doctor said, he's young. He has a strong heart. He's physically a strong guy."

Ford entered the hospital in Etobicoke on Tuesday evening after feeling unwell. He was admitted for overnight observation and had undergone a battery of tests, Ford's office said in a statement on Wednesday.

His office said he was resting and in good spirits. The mayor has previously had problems with kidney stones. He has also been trying to shed weight in recent months.

Earlier this year, Ford and his brother launched a public weight-loss challenge that raised funds for charity.