It’s actually much easier to see if a patient is a heavy smoker.
Heavy smokers are so addicted that they smoke all day, and so they smell of smoke during consultations (whereas high-functioning alcoholics often do not drink at all during the day). Heavy smokers also always have leather faces and deep raspy voices, and this stuff is virtually impossible to hide (while only some heavy drinkers have puffy faces, broken capillaries, poor body hygiene and beer bellies).
On the other hand, some signs may be red flags:
when the patient is drunk or reeks of liquor during a consultation;
some specific blood values might point toward alcoholism in the sense that patients who have drunk too much recently might have increased numbers (it is by no means a proof of general heavy drinking but at least an indication, and it’s the one which always red-flags me);
Korsakoff syndrome, baby: middle aged patients who hardly know where they are and seem to suffer from early-onset dementia (and actually don’t), but actually live in a nursing home because they forget most everything after two minutes and wear a diaper.
But for every bunch of typical patients, you’ll find one or two hard-core alcoholics which are highly functioning and which will only be “caught” if in the middle of the act.
And no, the bulbous-Johnny-Cash-nose thing is not necessarily caused by heavy drinking after all —
But it sure doesn’t help either.