Young drug addicts in South Africa are using a dangerous practice to share their high. It's nicknamed 'Bluetooth'.

Addicts inject themselves with heroin, then draw their own blood back up the syringe and inject it into a friend.

'Bluetooth' carries a high risk of transmission of HIV, hepatitis and other diseases. But many of the young people doing it say they no longer care about their lives.

Africa correspondent Sally Sara reports from the township of Diepsloot, near Johannesburg.

Warning: this story contains graphic content.

A man stands outside wearing a Qantas pyjama top, watering the dirt road to keep the dust down. I point at the kangaroo logo and tell him it's from Australia. He shrugs his shoulders and smiles. I don't know how the pyjamas got all the way here. It's a bit like the way many people end up in Diepsloot. No-one really planned it. But, once they are here, it's difficult to get out.

The township began in 1995. Its first residents were brought here from the riverbanks in Alexandra township in Johannesburg, where their shacks were at risk of flooding. The government promised them a better life, but it hasn't come true for most. The townhouses and malls of suburban Johannesburg are growing closer to Diepsloot, but in some ways their opportunities seem further away.

Young women sit on plastic crates, drinking beer and cheering on the Qantas pyjama man as he waters the street.

"Ay wena! Hey you. Come, you must clean my shack next," she says.

The other women clap their hands and throw their heads back in laughter. It's only 11:00am, but the smell of beer is already strong around the township on a Sunday. There are sharp divisions on this day of the week. The beer drinkers sit in circles outside their shacks. The churchgoers are dressed in white and blue robes, some carrying wooden crosses. Drink or pray — that's the choice.

But in a garage across the road there's something else going on. Three young men sit huddled around a flickering candle in a makeshift garage. There's something secretive about it. Part excitement, part fear.

Drug addicts (L-R) Thomas, Michael and Simon have been caught up in the dangerous drug practice. ( ABC News: Sally Sara )

The young men are drug addicts. Thomas, Simon and Michael. That's what we'll call them. They don't want to use their real names. They are thin, with deep voices and bloodshot eyes. One word rules their lives - nyaope.

The South African Department of Justice says, "It consists of a mixture of either heroin or dagga (cannabis) to which other harmful substances can be added.".

It can be smoked or injected, depending on its form. In its injectable form, it's heroin mixed with cutting agents.

Nyaope has flooded the townships. Dealers are on almost every street in Diepsloot. Temptation is never very far away.

"Within a 100 metres?" I ask.

"Yeah, basically 50 metres. Not even 50 metres," Thomas says.

Nyaope only costs 30 South African Rand a hit. That's less than $3. But, here in Diepsloot, even finding a few dollars a day is a mission.

Nyaope powder being prepared for injection. ( ABC News: Sally Sara )

"I sometimes steal. I sometimes play the dice. Hustling, you see, every day. Because without this I can't survive. I don't feel like I'm myself, you see," Michael says.

Thomas, Michael and Simon all had a hit of nyaope this morning. It was the first thing they did. Before they eat, shower, kiss their loved ones, they answer the call of nyaope first. It's the same every day, if they have the money.

Participants are usually willing to share blood because they are already desperate and have little regard for their lives. ( ABC News: Sally Sara )

They are calm, polite and articulate. The tail end of the nyaope high gives them confidence to talk. But they are not too high. They're already looking for another hit.

"Honestly with this thing, you don't have time for yourself. You only have time for it," Thomas says.

What they are about to do next could eventually take their lives. I'm nervous even sitting close to them. Our local fixer leaves the garage because he can't bear to watch.

Michael already has a thin length of rubber tube tightly around his arm. Thomas is giggling, running his fingers across the skin, looking for a vein. Both young men are excited.

This is 'Bluetooth'. One addict injects nyaope into his veins and then draws his own blood back up the needle and injects it into a friend. It's a cheap way to share a high.

"If a friend of mine has one. I can still still, like, rely on his blood. So that is why we call it Bluetooth because you take from his blood, that drug straight from his blood, and then into my blood vessel," Thomas says.

Dangerous risk for a fictitious high

Thomas watches as Michael's blood is injected into his arm. ( ABC News: Sally Sara )

Bluetooth is highly dangerous. It exposes the addicts to infection, HIV and hepatitis C. And the sad thing is that doctors say the shared high is all in the mind. Medically, it's unlikely there would be enough nyaope in the blood of one addict to trigger a high in another. So all that risk could be for nothing.

But Bluetooth has taken off amongst addicts in the townships. It's part desperation and part rebellion. A horrible act of self-destruction for those who feel uncared for.

"We worry later about the diseases. Actually we don't care about those. So, as long as we have the nyaope in our system, everything else comes afterwards, you see," Thomas says.

Michael, however, says he worries about the future "because I know what I am doing now is not alright".

"It's too heavy for me but already I'm in. I do worry. I need help to see myself outside these things," he says.

Michael exhales with relief as he finally finds a vein and flushes the nyaope into his blood system. He pulls out the needle triumphantly. Thomas and Simon nudge him. There is no time to relax just yet. They put the needle back in his vein and draw blood back into the syringe.

They move the candle closer to find the veins on Thomas's arm. By the flickering light, they inject Michael's blood into Thomas. They all look at each other with a sense of accomplishment. Freedom.

But reality is hanging right above them. A pink hat and a cartoon backpack belonging to Thomas's daughter are dangling from the clothesline. All three men are fathers. Just 28, 29 and 31.

The addicts, Thomas, Simon and Michael, are all young men with families. ( ABC News: Sally Sara )

"Most of us didn't go into the drug thing just for fun. As time went through, we find it as a substance to use and calm our difficulties like. Everything we went through, or everything we're still going through. So we mostly rely on it for, I can say, therapy," says Thomas.

"It mostly has something to do with the past. It depends mostly on how you were raised, because most of us are from such backgrounds."

Simon adds: "I started Bluetooth last year, February, when I heard my sister was passed away. Sometimes I sit down and think about it. But without my sister there is no way I can do it because there is no one who can guide me, show me the way. I'm alone now."

Thomas says the men use nyaope and bluetooth as a type of therapy. ( ABC News: Sally Sara )

Mob justice could kill addicts if drugs, disease don't

There are very few rehabilitation services available in the townships of South Africa. So once young people get hooked on nyaope, there is little chance of getting clean again.

It's not just the risks from the drug or infection, it's the community. In places like Diepsloot, the police are not trusted nor effective so people take the law into their own hands. If thieves are caught they can be beaten, whipped or even burnt to death if mob justice takes hold.

It's the one thing that scares the nyaope addicts more than anything.

In rough areas like Diepsloot, the stakes are particularly high for drug users like these. ( ABC News: Sally Sara )

"Here in our communities, this place is rough, man. So if they find you stealing they end up burning you," Simon says.

"When they see us, they don't see a future, you see. Like, we are nothing to them," Michael says.

Thomas says: "So even our dignity is dragged in the mud. So we can no longer be useful to the community."

Thomas, Michael and Simon hold little hope for the future. They fear that if the nyaope doesn't get them, the community will.

"Yeah, we do worry because death is just around the corner for us. Not only with the drugs, but how we get the money to buy those drugs," Thomas says.

"We are taking chances almost every day. It's a daily thing. So our lives are like, I for myself could say, my life is on the line."