How long have you known him for?how long has he been drinking?number of drinks?pattern-ie...daily?few x's a week?weekends?
Is He open to discussion?
Denial is a very powerful thing and very hard to break through but You should certainly approach the issue with Him.
IMO to think one is "self medicating" is an 'excuse' for why one might have a 'problem' with alcohol - people become addicted to alcohol because it is an addictive substance - and is also a destroyer of mind, body and relationships