Anemia is common in critically ill cats. The origin may be either acute or chronic. The diagnostic workup for cats with acute anemia should include the following: evaluation of blood smear, slide agglutination test, complete blood count, new methylene blue stain for Heinz bodies, Coomb’s test, blood typing, FeLV/FIV testing, chemistry panel, coagulation testing (if evidence of bleeding) and PCR for hemotropic mycoplasmas.