Ford, 45, pulled out of the mayoral race last month after he was diagnosed with a rare and aggressive type of cancer, opting instead to run for council.
He has taken time between his chemotherapy treatments to campaign for his brother — Coun. Doug Ford — who is one of the three main contenders for the city's top job.
Ford said outside the polling station in Etobicoke that he feels tired and "not very good."
When asked whether the chemotherapy was working, he replied, "I don't know, I don't know, I don't know."
Ford said he is returning to hospital Oct. 29. His office said the mayor would be meeting with his doctors to review his condition and determine the next step of treatment.
Doug Ford says he wants to become mayor so that he can continue the work he and his brother began four years ago.
Rob Ford again urged his supporters Tuesday to vote for his brother, saying Doug Ford will be "the best mayor the city's ever had."
Note to readers: This is a corrected story. An earlier version said Ford would undergo another round of chemotherapy on Oct. 29.
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