Several biochemical tests are available to screen for heavy drinking in patients. Most of these (e.g., liver function tests and macrocytic volume) rise due to adverse effects of alcohol on organs or the organ's functions. Carbohydrate-deficient transferrin, however, seems to elevate because of the direct action of alcohol or one of its metabolites. A second valuable contribution of biomarkers is identification of relapse events in recovering alcoholics that either would not be voluntarily reported or reported only much later. Finally, providing feedback to patients in treatment based on their biomarker values and changes in them during the course of treatment can enhance motivation, a key component in recovery from alcohol problems. The current article offers a clinical rationale for routine use of biomarkers of heavy drinking in health care practice and proposes recommendations on how they might be best used.