Why are you asking?
I am addicted to ketamine; although it was somewhat worse last year then it is now I would probably still have to call it being addicted. For me it started by trying ketamine after being very curious from a more psychedelic point of view as drugs I did before that were mushrooms, LSD and nitrous oxide, from then on it became a once every two to four weeks kind of thing, occasionally two times in one week too but sometimes a month or more would pass; I had no tolerance at all in that time a gram would litteraly last me four or five months. I tried it the first time very early 2009; around spring 2011 usage had gone up to every two weeks or even week and tolerance had gone up to a gram only lasting about a month. Somewhere around then I decided to try and use ketamine every day for a week as an experiment of kinds; an experiment with addiction in a way actually. After that I got the brilliant idea 'lets get 10 grams; that'll last me almost a year'; which in reality lasted me about a month, that's how fast tolerance was rising by this point. All of that summer I did ketamine daily most of the time occasionally taking a one week break or so but it had gotten quite daily by the end of it with tolerance up to nearly a gram in a dáy. Then there was this two week period in which there was no K; was a huge discussion about it in the bluelight europe subforum too since that was apperantly all over europe; when it returned tolerance had gone down due to the two week break but I instantly started doing it daily again. Then later that autumn 2011 I first experienced K-cramps; holy fucking shit that gave a new dimension to pain.
I'll skip ahead time since you can assume I did ketamine atleast 2-5 days a week for quite some time, sometimes brief periods of daily or nearly daily. Móre then a gram in a day started to become normal; with records of up to 5 grams in a day and K-cramps started comming more often too. Around summer 2012 I did ketamine every day around 3-4 grams for a month and ended with peeing blood and a hospital visit weigting only 43 kg at 1.76m (I had also done some speed that summer); after that I decided never again absolute daily use; it was constant K-cramps (which I had atleast once a month anyway) and then just doing more K on top of it to cover them up and starting to get bladder pain and then doing more K to cover that up to eventually snortings grams in a day while watching yourself fall apart nearly litteraly. Very fucked up stuff. So yes then early autumn 2012 I went back to just weekend use which still consistent of doing serveral grams every weekend but no more K-cramps and for a while no bladder issues either. Those did come back but that was around midwinter and around then I did fentanyl for a month; and soon after that went to costa rica for a month where I did no K at all; since I'm back I háve been doing it on the weekends but the compulsion of the addiction broke. Its not as compulsive and I've taken a good look at issues in my life since for me doing K was for a big part just about escapism; and I did not know what I was fleeing from but basically I was trying to be an escapist from my life itself; I changed the plans I have for the future but really I don't want a life without dissociatives. I do not want a live without ketamine. I really know for a fact that I WANT to do it atleast once a month, although maybe not every week and it would be wonderful if I would be capable some day to keep it around and not do it all, now I have to get me some more every time I want it since I can't keep it lying around and nót do it; but just being strict in not buying too much at the start of the weekend makes it doable.
By the way always nasal (I do think I may have a tiny hole high in between my nostrils, I'm not sure and I'm sort of scared about that) but other then that no harm has come from how heavily I abused it the past few years; my bladder and kidneys are both healthy and fine, I've only had K-cramps once since like oktober and especially since that sober months in costa rica, even though I do ketamine about every week its nothing like it was, I'm hoping to get down, just by will power, back to once every two weeks because tolerance wise, that'd be a bit healthier.
The compulsion to do more once properly deeply addicted is insane; I snorted it off the floor, have many times searched my room for hours if there wasn't the tiniest remaining bit; if I have money I wíll typically get more ketamine, unless its early midweek; and if I get offered I can't ever say no. That last also goes for nitrous oxide; I just really love dissociation; really really love it; the K-holes are my favorite and the absurdistic way of thinking, how it feels on the body, I just love it. Its really, really my drug of choise in that aspect.