Peer is acting mayor after mayor Zandile Gumede took a 30-day leave of absence following her arrest over charges related to a R208mn Durban Solid Waste tender.
It is understood that Peer rushed to a Durban hospital accompanied by her bodyguards.
Calls to Peer went unanswered.
However, in a statement the city denied the acting mayor had been poisoned.
"eThekwini Municipality would like to refute allegations that Acting Mayor, Cllr Fawzia Peer has been poisoned.
"At this stage we can confirm that Cllr Peer complained about the taste of the water she had consumed. For precautionary measures she went to the doctor for a check-up. The water she consumed has been sent to the laboratory for testing."
The city said they would await the laboratory results and the doctor's report before "making any conclusion on the matter".