Little is known about the prevalence of hematologic abnormalities in adults with severe anorexia nervosa. We report the first major analysis of hematologic dysfunction in such patients. We retrospectively analyzed the charts of 53 men and women with severe anorexia nervosa, admitted between October 2008 and December 2010 for medical stabilization to our center, which has a national referral base. Patients were predominantly female (89 %), with a median age of 28 years (range 17-65), and were hospitalized for a median duration of 15 days (I.Q.R. 9-29). Nadir body mass index during hospitalization was markedly low at 12.4 kg/m(2) (range 8.4-15.7), and the mean discharge BMI was 13.8 kg/m(2) (range 10.2-16.8). 83 % of patients were anemic (hematocrit <37 %), with only 3 (6 %) having iron deficiency. 79 % were leukopenic (WBC < 4.5 k/μL), 29 % were neutropenic (ANC < 1.0 k/μL), 25 % were thrombocytopenic (platelets < 150 k/μL), and 17 % of patients developed thrombocytosis (platelets > 400 k/μL) during their hospitalization. Eighty-nine percent of patients had resolved their neutropenia by discharge. Marked hematologic deficiencies are often present in patients with severe anorexia nervosa, generally attributed to starvation-mediated gelatinous marrow transformation which resolves with proper nutritional rehabilitation. Improved provider awareness of this association may reduce unnecessary testing and costly treatment interventions.