Carbohydrate-Deficient Transferrin (CDT), % details

This test measures an abnormal form of transferrin (the iron-carrying blood protein) that increases specifically with heavy, sustained alcohol consumption — generally several drinks a day for at least a week or two. Unlike standard liver tests (like GGT or AST/ALT), which can be elevated by many different causes, elevated %CDT is fairly specific to significant recent alcohol intake, making it useful in situations where an objective marker of drinking is needed, such as certain medical, legal, or occupational evaluations. It isn't sensitive to light or moderate drinking and typically normalizes within a few weeks of abstinence, so it reflects fairly recent, heavy use rather than lifetime drinking history.