I'm not a man, so maybe you don't want my input here; but I've often found that the way I think seems to be the way men tend to think. So, for what it's worth: My thinking is that a person usually has a pretty good idea that he's drinking more than he should, and doesn't want anyone else pointing out to him what he already knows (but can't/won't do anything about).
Saying something like, "I'm kind of concerned at much more you've been drinking lately," may not be particularly offensive to the person; but if he's an alcoholic he's most likely going to say, "It's fine. You don't have to worry about it," or else, "I know. I'm planning to cut down after.....".
If s/he is drinking so much it's affecting your day-to-day life, I think you ought to present that angle to the person. I think that angle is the one he'll most see as "your business" and something you have a "right" to be concerned about.
Other than that, maybe just ask, "Do you think maybe you're drinking is starting to become a problem?" He may say, "Yes, I think it may be, and....." or he may say, "No." Either way, you take some risk of making the person irritated/angry at you, but approaching him to his face (rather than talking behind his back) is, I think, always better.