Anemia is a common hematological alteration in cats. The objective of this study was to evaluate the frequency of different types of anemia and the course of disease in cats with a hematocrit (hct) < 0.26 l/l. In a period of 18 months 194 cats were included and assigned to different anemia groups based on history, physical examination and laboratory parameters. Most cats had acute blood loss anemia (BA; 75/194; 38.7%). Frequent causes were trauma (39/75), hematuria (13/75) and hemostatic disorders (9/75). Anemia of inflammatory and neoplastic disease (AID) occurred in 22.2% (43/194) and hemolytic anemia (HA) in 18% (35/194). Half of those were presumptively immune-mediated (IHA). Four cats were diagnosed with hemotropic mycoplasma infection. Rare causes of anemia included anemia of renal disease (ARD; 18/194; 9.3%) and intramedullary non-regenerative anemia (INR; 13/194; 6.7%). The latter either had retroviral infection (6/13) or neoplasia (6/13). In cats with HA and INR anemia was often severe and very severe (Hct < 0.14 l/l) and in cats with AID and ARD usually mild (Hct 0.20-0.25 l/l). Cats with BA had significantly lower total protein concentrations than those with INR (p = 0,001), HA, AID and CNE (p < 0,001) and those with HA most often had hyperbilirubinemia (21/27). Blood transfusions were primarily given to cats with BA (37/75) and HA (19/35), especially those with IHA (13/17). 69% of the patients survived the first 14 days after the anemia was detected for the first time. Cats with HA had the highest survival rate.