Bacterial cultivation from patient samples is the foundation of proper antibiotic treatment. A frequently used cultivation medium is agar with an additive of blood, so-called blood agar. The recommended additive of blood is horse blood while human blood is currently used as an additive at the microbiological laboratory Ryhov, Jönköping. The study aimed to evaluate horse blood in blood agar prior to a change in blood from human to horse blood according to a regulation from the European Union. The method consisted of cultivation from reference strains, clinical isolations and clinical patient samples on both blood agar with human blood and blood agar with horse blood. The comparison included a visual assessment for both blood agar based on the criteria of haemolysis, colony size and bacterial growth. In the assessment of clinical patient samples, in addition to the previously mentioned criteria, mixed flora was also assessed. The study resulted in a more distinct demonstration of haemolysis on blood agar with horse blood than on blood agar with human blood for haemolytic bacteria. An equivalence for both blood agar was presented regarding the remaining criteria. Based on these results a change can be made according to the regulation without negative impact.