I first took ketamine in 2002, between my second and third years at university. I was mourning the end of a long-term relationship with a massive bender. It was a weekday afternoon and I was necking ecstasy and playing pool when a mate asked me if I'd ever tried "K".

We didn't even finish the game. We went back to my flat and it was love at first snort.

One of the problems with K is trying to explain what a "K-hole" is like. Nothing can prepare you for the chaos. All you can say is that it is really weird, but until you have taken it, even the most drug-fried mind can't comprehend what "weird" can mean. Most people hate it; it's just too much. Many are sick because of a sort of mental travel sickness. But I didn't throw up: I adored it.

The K-hole has been described as an endless dimension to explore, and that's exactly what it is. Space, time and language either have no meaning or become ridiculously distorted. It can seem as if you are travelling through time or seeing into the future, as if you are living multiple lives or not living at all. And you feel something coming, something huge with you at the centre, because there is a massive messiah complex in there as well.

I have been at one with the cosmos, communicated with the universal forces that are our true gods, and been told that death should be embraced as the next level of everything. All complete bollocks, of course, but I never got that from a wrap of coke.

For a little while I had my ketamine use under control and found it therapeutic.

K - which was originally developed as an anaesthetic and is still used to treat animals and occasionally humans - did wonders for my ego. I lost my sense of shame and fear of death, I felt liberated. I got an unexpected first at uni, I was writing book reviews for a national magazine, and I had a new, beautiful girlfriend. I hung out with fellow K-heads, or "wrong 'uns", as we were known to other druggies, whose company I loved. I felt part of something and life was good, but all the time I was using more and more K.

It is the tolerance that gets you. When you start, a gram might see you through three or four nights out. Before long it will be enough for only a few hours and, sooner or later, you start using it at home. I started selling it to pay for my habit.

Today, ketamine is a class-C drug, on a level with cannabis, but until a few years ago it was regulated only by the Medicines Act, and although it was still illegal to deal in it, the police took less of an interest. I used to buy it in liquid form and then cook it in a pan or microwave to create powder. The liquid came from India, often disguised as rose water. Someone would have it posted to their house and I would buy a litre from them for £300. That litre would turn into 50 grams, which I sold for £15 or £20 a gram. It never felt like a risk, at least as far as the police were concerned. But I couldn't have that much K around me without doing it, all the time.

If I wasn't at work - I had become a chef after leaving university - I was taking K.

I would take a gram during the break in my split shift. I would get home and sniff three grams in front of the television, and then take another three to bed with me. I had a line before work, not knowing if I had slept. And I was starting to get ill. I have always liked drink and drugs but, other than tobacco, I had never been truly addicted to anything before. I never used heroin or crack, and could tell when any substance was becoming a problem. I usually just got bored of something and moved on - but not this time. K may not be physically addictive, but it is compulsively psychologically addictive.

I stopped dealing when my girlfriend asked me to, hoping that this would help, but I was too far gone. I still did as much, but I started to hide it from her.

After about two years of using ketamine, I was spending more and more time in the toilet, and urinating was beginning to hurt.

I developed a stoop because my penis was always burning. One day, on a train, I had my first cramp attack; I thought my lung had collapsed. I went to a doctor, who told me to stop taking K or I would die, but then an older user told me not to worry, it was "just K cramps". He said that they wouldn't kill me, but I might wish that they would. Apparently they could last for days.

I still didn't stop. The cramps got worse, the blood and mucus began to appear frequently in my urine and I had to pee every 20 minutes. I lied more than I told the truth, particularly to my girlfriend, and I hated myself. I couldn't stand to be around myself and wanted to cause myself harm. K worked on both fronts.

I stopped going out because my friends didn't want to see me like that, I quit my job because I was in too much pain to work, and I lost the review gig because I could no longer read a book. I fell further into debt.

By the time I realised that ketamine was ruining my life, I no longer cared. I didn't want to die as such; I just didn't mind if I did. My girlfriend couldn't save me. She begged me to leave the west country town where I was living, surrounded by other K-heads, and move back to Devon, where I had grown up.

I told her I would, but I was lying. I didn't want to give up. I was positive I was going to die whether I did or not.

One evening, about a year ago, when I was supposed to be watching a friend's band play at our local, I found myself naked, writhing on my kitchen floor, racked with abdominal cramps and self-loathing, and praying.

Praying to a God I don't believe in to show Himself, to intervene, to give me something to believe in other than ketamine, and the certainty that my life was over. He didn't, but when the pain subsided, the relief was almost like a drug in itself.

In the end change was forced on me. A local street gang had tried to break into my flat on several occasions. They held a knife to my flatmate's throat as he left for work. We managed to fight them off, but I could hardly walk by then and weighed nine stone. It was the street or home. I called my mum.

Once back home, I could barely sleep and suffered from night terrors and sleep paralysis. I started to smoke cannabis, scored black-market codeine and Valium. And I kept begging my K dealers to send me some. I offered them silly money, but they still said no, because they truly were worried about me. Later, when I did find another source of K, I used the bare minimum to get me through the craving.

So here I am, living on my mum's settee. I've got my health back but lost everything else, including my girlfriend. She had lost all trust, and in the end she realised she would be glad to see the back of me.

Do I think that ketamine should be higher than its class-C listing? No, but people should know what they are dealing with. By the time I did, it was too late. There is so much media coverage of illegal drugs, yet K is rarely mentioned, although it is everywhere and spreading fast. Most people who try it won't develop any major problems, but a minority of users get very sick. A friend of mine lost so much control over his bladder that he had to have a catheter fitted when he was 21, and there are going to be a lot more cases like this. He didn't know it was addictive either.

The one bright spot in all this is that the human body has amazing powers of recovery. If there is any addict of any substance reading this who thinks that they have destroyed their body beyond hope, you might be surprised what happens if you give it a break. Within a month of moving home, I got a job as a builder. I even pee like a normal person. Do I drink too much and smoke too much pot now? Yep. Do I still crave K when I'm down or depressed? Sometimes. Do I ever give in to those temptations? Never. Am I still a liar? Of course not, darlin', I promise.

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