As with all recreational drugs, it is difficult to know exactly what the ketamine you are taking actually contains. Doses found in street drugs are not controlled. The amount of ketamine you are taking could be much higher than you think. In addition, ketamine is often 'cut' with other substances, which might be poisonous, or with other drugs, often amphetamines,
LSD, and sometimes heroin.
Because of its anaesthetic effects, ketamine can stop people feeling pain. There have been reports of people suffering severe internal injuries after being fisted whilst taking ketamine. Sexual inhibitions might also be lowered by taking ketamine and there is some anecdotal evidence that use of the drug acts as a trigger for unprotected sex for some people.