How to step in when Drugs are involved?

My Uncle was an alcoholic, and did meth. He would go to his house and abuse himself for months then come out for a few weeks to sober up and do it again. This went on since I was 4 yrs old, as I grew up I started a friendship with my uncle because we were both sort of outcasts in our family. I took it upon myself to help him over his diseases, I would go over to his house clean him up take the boose and meth away, I did this for years, and he never changed. I left for canada when I was 17 to be with the love of my life, shortly after I left he died, I tried my best I loved him so much, but the minute I wasn't their he died. I blame myself for leaving and it really hurts to think of him now. If I could of done things differently I would have made a bigger support circle around him, let him know all the time that he was loved, and I would have held in their until he was better for good. But dont take it just upon yourself you need as much help as you can get. Im so sorry you have this burden, I wish the best of luck to you. - Paul