To dream that you are using some kind of illegal narcotics, means that you are not feeling yourself anymore. Probably there is something that makes you feel dizzy, angry or even sad. Make sure you change the situation or whatever makes you feel that way. If someone is trying to give you the illegal drugs, it means that there is someone in your waking life that gives you a bad influence. If you are using some kind of prescript drugs and forgot to take them while dreaming, it shows that you do not take enough of the responsibility of your life.
Read more about dreaming of Narcotics in other dream meanings interpretations.