I Need Some Guidance Please

My son is 28 years old and insulin dependent diabetic since 14. He is a rx drug abuser, oxycontin, morphine and anything else he can get. He will take anything for a high and to be numb. His true favorite is Xanax. He did take the step and contacted outpatient treatment and goes every day at 5am to methadone clinic. He functions and has a job. It has been one month since starting methadone and was doing well----until about week ago and he is self medicating in the evenings with alcohol and Xanax mixture along with the methadone. I have been staying with him and making sure his blood sugar does not drop too low. I cant keep doing this but don't know how to stop. I tell myself if he wasn't diabetic I would not do this but I know I am probably making excuses also and enabling him. He is still lying and telling me he not doing anything when I can smell alcohol and he can not walk straight. What to do?
You will read your story in these threads repeatedly.

I hope you see the problem clearly and take appropriate action.

Al-Anon and Nar-Anon would help you immensely if you attended their meetings.

I wish you the best.

Bob R