Abstract OBJECTIVES: To identify the causes of anaemia, other than acute blood loss, in dogs and to determine whether severity of anaemia provides clues to the diagnosis. METHODS: The veterinary medical database of the Veterinary Campus Hospital, Lyon was searched. Dogs with anaemia (packed cell volume <37%) were included and assigned to different disease groups. Dogs with acute blood loss were excluded. The case records were examined for weakness at presentation, the severity and regeneration of anaemia and the final diagnosis including tumour type if applicable. RESULTS: The case records of 456 dogs with low packed cell volume were included. Cancer-related anaemia and anaemia of inflammatory disease accounted for 33·1 and 28·5% of cases, respectively. Most dogs with cancer-related anaemia had solid tumours (73%). The prevalence of immune-mediated anaemia increased with severity of anaemia (5·3, 15·5, 41·2 and 56·2% for mild, moderate, severe and very severe anaemia, respectively), whereas the prevalence of anaemia of inflammatory disease decreased (36·7, 22·5, 2·9 and 0% for mild, moderate, severe and very severe anaemia, respectively). CLINICAL SIGNIFICANCE: Anaemia of inflammatory disease and cancer-related anaemia were the most frequently identified causes of anaemia in dogs. The percentage of dogs with immune-mediated anaemia increased with anaemia severity, whereas the percentage of dogs with anaemia of inflammatory disease decreased with anaemia severity. Thus, severity of anaemia may provide clues to the diagnosis.