Some friends will understand and some won't. In fact, some of your friends might be in denial about their own problem and are therefore not able to support you since it would force them to analyze their own behavior.
I found that making new friends was the best option. I was entering a new chapter in my life and found that now that I was giving recovery everything I had the types of friends I had when I was using just didn't fit into my new lifestyle. We had different goals in life and it would have been unfair for me to expect them to change.
I found friends that don't use drugs and it was refreshing. I even got rid of my old friends that were supporting me because there was always a chance they could tempt me. Also, I associated using with those friends so even if they didn't try to tempt me they could still be a trigger for me.
Do what you feel is best for you and your recovery. Don't be afraid to find new friends and accept that you are moving into a new phase into your life and that requires change.