By Duncan Middleton
Newsbeat reporter, Bristol
Ketamine may not be as common as cannabis or cocaine but there are fears it's becoming more popular. A drugs charity's warning more people are experimenting with larger doses and beginning to inject it. Newsbeat's been to Bristol to find out more.
Richard is a recovering drug addict.
He's spent years living in squats but now has a small flat of his own.
Sitting in a greasy spoon cafe with a cup of tea and bacon sandwich, he thinks ketamine has become less expensive recently.
He said: "I think it's a worry because I don't think many people really know the risks of taking ketamine at the moment."
Ketamine's been quite an underground drug until now. And that's backed up by the charity DrugScope.
It says it has evidence that more people are taking the drug and they're taking bigger doses. That's why more problems are being reported.
Jim Bartlett's been working at the Bristol Drugs Project from more than 10 years.
People can be very vulnerable and forgetful when they're on ketamine. So you're more likely to get robbed or sexually assaulted
Jim Bartlett from Bristol Drugs Project
He says he's noticed more ketamine users coming in and asking for help.
"Sometimes, from only using it for six months, people are getting urological problems. They're having problems weeing, they're in lots of pain. You can get something called the K cramps which is severe and lasting abdominal pain.
"We even had one girl who had to have major reconstructive surgery on her bladder after taking ketamine," he said.
But Jim warns that it's not just the physical effects: "People can be very vulnerable and forgetful when they're on ketamine. So you're more likely to get robbed or sexually assaulted."
Ketamine's usually smuggled into the UK from India where you can buy it over the counter.
It's colourless and doesn't smell.
In 2006, the Government made it an illegal substance, making it a Class C drug, the same level as anabolic steroids and cannabis.