Miles LF, et al. - Considering that preoperative anaemia is typically diagnosed with a haemoglobin concentration < 120 g.l⁻¹ for women and < 130 g.l⁻¹ for men based on limited evidence, researchers conducted this retrospective cohort study to stratify women undergoing elective, major abdominal surgery based on preoperative haemoglobin concentration: anaemic (< 120 g.l⁻¹); borderline anaemic (120–129 g.l⁻¹); and non-anaemic (> 130 g.l⁻¹). Data were analyzed from 1554 women. After multivariable adjustment for procedure, Charlson comorbidity index and patient age, a negative link between logarithmic preoperative haemoglobin concentration and duration of stay was observed (parameter estimate (standard error) −0.006 (0.003) vs. 0.003 (0.003) for a haemoglobin concentration < 130 g.l⁻¹ vs. > 130 g.l⁻¹, respectively); the difference in duration of stay was about 50% greater for women with a haemoglobin concentration of 120 g.l⁻¹ vs those with a haemoglobin concentration of 130 g.l⁻¹. Although the relation of borderline anaemia to postoperative complications is unclear, it is important to re-evaluate the existing diagnostic criteria.