Be open and ask but be prepared with information and a plan of what to do next. Addiction is a disease of denial so be prepared for that. You can have an informal intervention which is a conversation or a formal intervention with professional and other important family members. You can find a guide to Intervention, "Time to Act" from the Partnership for Drug Free America website.
Teaming up with an addiction professional can get you help they need. Please refer to the Office of Alcoholism and Substance Abuse Services (OASAS) website for a listing of certified programs/professionals or call OASAS addiction services helpline 877-8-HOPE-NY or Nassau County Department of Drug and Alcohol 24-hour hotline number 516-481-4000. Nassau Alliance for Addiction Services (NAFAS) at the NAFAS website.