Introduction: Anaemia contributes to increased morbidity and mortality in hospitalised patients, yet unnecessary blood tests from inpatients may actually induce a “hospital acquired anaemia” (HAA). This study examines the incidence of phlebotomy-induced anaemia during a hospital admission. Methods: Patients admitted to the Royal Bournemouth Hospital between 2009 and 2011 for a period of more than two weeks were identified. Those with normal haemoglobins on admission (Hb > 130 g/dL in men; Hb > 120 g/dL in women) were selected to be included in the study. One hundred and sixty two patients were randomly selected from this group and their admission and discharge haemoglobin was recorded, and the change in Hb was calculated. The number of blood tests taken during admission was calculated from each patient from which volume of blood lost was determined. Age, sex and co-morbidities, bleeding complications and blood transfusions were noted. T-test for unequal variance was used for analysis. Results: Of the 162 patients, 69 (42.5%) developed a HAA (defined as haemoglobin drop from normal to <110 g/dL). The average number of blood tests taken in the anaemia group was 37, compared to only 23 in the “no-anaemia” group. i.e. 132 mls in the anaemia group vs. only 80.2 mls in no-anaemia group. Further analysis of the anaemia group revealed that 40 patients developed a “mild anaemia” (defined as drop in Hb from normal to <110 g/dL) and 29 developed a moderate/severe anaemia (drop from a normal Hb at admission to <100 g/dL). Significantly higher volume of blood was withdrawn from this moderate/severe anaemia group compared to those that developed a mild anaemia 177.9 mls vs. 121.34 mls (p-Value 0.007, F = 0.001) 95% CI 2.08 to 9.22. Conclusion: This study suggests that patients admitted for inpatient stays of more than two weeks may be at high risk of HAA as a consequence of diagnostic blood loss. This anaemia in turn may have detrimental consequences, especially in patients with pre-existing cardio-respiratory disease. There needs to be increased awareness of the risk posed to patients as a result of diagnostic phlebotomy and further studies are required to study its impact on LOS, morbidity and mortality outcomes.