I might lose one of my best friends
What is the reason why you may loose one of your friends?
Yes, he needs treatment for his condition
It's good to try to maintain important relationships in the face of hardship.  If you can, do anything possible to help your friend get treatment, but even if you can't, just being there for him will be a source of comfort for both of you.
I think I'll lock myself in my home.
While it may be difficult to see your friend like that, you should really make an attempt to see him. Locking yourself in your room will not do any good. Maintaining your relationships can sometimes take effort.