Anaemia is a common clinical condition but not a ‘definitive diagnosis’. The first priorities in anaemic dogs are to characterise the anaemia and determine the major differentials. A systematic approach to investigating anaemia enables the cause to be identified, effective prognostication and definitive treatment (if possible) to be provided. It is important to determine the character of the anaemia as soon as possible as this determines the most appropriate investigations and treatment. For example, there is nothing to be gained by performing a bone marrow sample in a strongly regenerative anaemia and nothing to be gained from high doses of immunosuppressive medications in anaemia of inflammatory disease.