Hundreds of people may have been exposed to HIV and other infectious diseases after being treated at a hair replacement clinic in Sydney's CBD.

The South Eastern Sydney Public Health Unit has found there was poor infection control at Doctor Angela Campbell's Macquarie Street clinic between December 2010 and February this year.

An investigation by authorities found there were problems with the cleaning and sterilisation of surgical instruments and equipment at the clinic, and concerns had been raised by neighbours in the building about the disposal of medical waste.

Dr Campbell's medical registration was suspended in late February and the case is being investigated by the Medical Council of New South Wales.

Professor Mark Ferson from the South Eastern Sydney Public Health Unit said there could be a few hundred people who need to be tested.

"We believe the risk is low but this is precautionary measure to warn patients of Dr Campbell's clinic they need to go to their doctors to be tested for Hep C, Hep B and HIV just as a precaution," he said.

He said anyone treated at the clinic between December 2010 and February of this year should consult their GP, or contact the public health unit to discuss the recommendations.