Objectives: The aim of this study was to determine the frequency and type of anaemia in adult patients with inflammatory bowel disease in the Eastern Croatia. Furthermore, the aim was to examine whether there is correlation between the incidence of anaemia and the value of C-reactive protein in patients’ blood, which could be considered an indirect indicator of the inflammation. Participants and methods: The study is organized as a cross-sectional study, i. e. cross-section and prevalence survey method. The study included 78 patients with IBD from Eastern Croatia 22 – 69 years of age. The following laboratory analyses for the detection of anaemia were used: serum levels of iron, transferrin, ferritin, TIBC, UIBC, C-reactive protein, complete blood count and reticulocyte count. Results: comorbidity present in 24.4% of patients with inflammatory bowel disease in Eastern Croatia. Anaemia was present in 24.4% of the subjects. According to the type of anaemia, in 63.2% of cases it is sideropenic anaemia, and in 36.8% of cases the chronic disease anaemia. Statistically significant differences were not found in the frequency and type of anaemia in patients with Crohn's disease in relation to patients with ulcerative colitis. In patients with active illness, there is a statistically significant increase in the presence of anaemia in relation to patients with inactive disease. Conclusion: Anaemia is a significant extra-intestinal complication of inflammatory bowel disease and in the absence of the treatment of anaemia within the inflammatory bowel disease it is a significant additional symptom or complication in the affected population.