BACKGROUND This study was done to determine the prevalence of folate deficiency and macrocytosis in patients admitted to the hospital medicine service with alcohol and nonalcohol-related illnesses. METHODS Two groups of patients, with and without alcohol-related illnesses, were included. Patients were excluded if they received folate therapy, medications known to alter folate concentrations, or if they had an uncertain diagnosis. Complete blood count and erythrocyte folate concentrations were determined from each patient. A Fisher's Exact Test and odds ratio were used to determine the prevalence of macrocytosis and correlation between folate deficiency and macrocytosis in the alcoholic group, respectively. RESULTS Of the 36 alcoholic patients, 11.1% were folate deficient, and 33.3% had macrocytosis. Only 2 of 12 patients with macrocytosis were folate deficient. No control patient had macrocytosis or folate deficiency. CONCLUSIONS The prevalence of folate deficiency among patients with alcohol-related illness is low. There is no correlation detected between macrocytosis and folate deficiency. Our findings suggest that it may be inappropriate to routinely supplement all alcoholics with folic acid, but certainly a small minority may benefit from it.