Metformin Interactions

Patient: I am writing because I am curious about the diabetes medicine I am taking called Metformin. I have been on it a little bit over a year and have been working hard at dropping weight to reverse my diabetes. My question has to do with certain things that interact with the Metformin. I don’t drink, I haven’t had an alcoholic beverage since December 23rd, 2010. I didn’t continue because of the interaction with Metformin and getting the Acid Lacidosis (I don’t know how to spell it haha). My problem is though that I hang around people who indulge in marijuana from time to time. The smoke does not bother me, but I feared that the smoke and thc in the marijuana might interfere with the Metformin. I won’t lie, I take an occasional drag from time to time, but over the past 8 or 9 months I stopped because of the fear of interaction. Is there any harm in breathing in smoke with Metformin in the body?