Objectives To evaluate improvements in laboratory markers of anaemia (haemoglobin, haematocrit, serum iron, and ferritin) in women with subjective heavy menstrual bleeding (HMB) treated with the levonorgestrel 19.5-mg intrauterine device. Materials and methods We conducted a pilot study at the Department of Obstetrics and Gynaecology, University of Campinas, Faculty of Medical Sciences, Campinas, SP, Brazil. We compared anaemia markers in 73 women aged 18–48 years suffering from HMB, one year after placement of the IUD. Results The mean age of participants was 30.0 years (range 24–38); more than half were white, and the mean body mass index (kg/m2) was 27.0. Twenty (27.4%) participants exited the study due to loss to follow-up (n = 12; 16.4%), expulsion (n = 7; 9.6%) and uterine perforation (n = 1; 1.4%). One-year post-IUD placement, amenorrhoea was reported by 10 (13.7%) women. According to intention-to-treat and per protocol analyses, the proportion of women with normal haemoglobin levels significantly improved (p = 0.014 in both analyses), as did haematocrit (p < 0.001 in both analyses) and serum iron (p = 0.003 in both analyses) compared to baseline evaluations. The proportion of women with normal ferritin levels also improved (p < 0.001) in both analyses using a cut-off of 15 ng/ml, though no significant difference was observed using a 30 ng/ml cut-off (p = 0.083 in both analyses). Conclusion The levonorgestrel 19.5-mg IUD effectively improved laboratory markers of anaemia one year after placement in women with HMB.