The former heroin user doesn't remember much about his overdose, but knows he was saved by workers from the centre.

They then helped him kick his 20-year addiction with a "miracle injection" of Buprenorphine, which can reduce withdrawal symptoms for weeks at a time.

"A lot of people want this centre gone. Now, drug abusers have been here regardless, this centre is helping drug users," Mr Melki told reporters on Monday.

The cancer survivor met his partner at the facility and the couple is saving up to buy a house and have a baby, which Mr Melki says is only possible thanks to the help he received.

Reporters were given a tour of the facility as part of the Harm Reduction International Conference, a global forum discussing best practice in drug use and harm reduction.

The North Richmond centre in inner Melbourne is now permanent but it remains controversial, particularly due to its location next to a primary school and continued public drug taking in the area.

The medical facility is decked out with fairy lights and colourful posters, including one showing 800 lives have been saved by Naloxone, a medication that can reverse overdoses, while another shows 323 people were treated for Hepatitis C.

Officially, about 60 lives have been saved there, but the centre's medical director Nico Clark says that number doesn't tell the full story.

"This service has been incredibly successful in reducing overdose and in helping people receive the support that they need," Dr Clark said.

"We can hardly even keep up with the demand from the local Richmond drug area."

More than 6000 people have used the facility since 2018 and about 300 people visit daily.

About 95 per cent of drugs injected is heroin and users must supply their own substances.

The average age of clients is 43. Most were first introduced to the drug by the age of 16 but some first tried it as young as six.

One user, who wished to remain anonymous, said it was one of few places she felt comfortable.

"I just feel safe here, I know I am not going to die in an alleyway," she said.

After injecting, clients can have a hot drink or toastie before heading to the medical facility, which includes a hepatitis C testing area, medical and dental practitioners and access to other services.

Harm reduction practitioner Sarah Hiley worked at Sydney's injecting room before moving to Melbourne and is shocked her clients still face stigma and discrimination.

"Walking into our building and being treated like normal human being is a unique experience for them," Ms Hiley said.

There were 50 heroin-related deaths in the local council area in the 42 months since the facility opened, down from 68 during the preceding 42 months.

Dr Clark says he wants to provide extra services like housing and backs the push for a second injecting site in inner Melbourne, which also attracted controversy.

It was due to be built near the Queen Victoria Market but former Police Commissioner Ken Lay is working on a report examining a different second location, which could be near Flinders Street Station.

Australian Associated Press