In mammals, icterus or jaundice is due to increased amounts of bilirubin pigments in plasma as a result of liver disease. Birds do not have bilirubin, therefore they do not become icteric if they have liver disease. Sometimes the plasma appears pink in color. This is due to hemolysis which is the breaking apart of RBCs and the subsequent release of red hemoglobin molecules into the plasma. Hemolysis is most commonly caused by improper handling of blood samples, such as forcibly expelling blood through the needle of the syringe, shaking rather than simply inverting the tube to mix blood with the anticoagulant, over centrifugation, or freezing and thawing of the sample.
Some toxicities can cause lysis of blood cells, the most common example being lead poisoning.
Occasionally an overwhelming infection causing septicemia will also cause hemolysis. The plasma can also appear white or milky in color, which is due to the presence of fat. This is called lipemia. Sometimes if the bird is excessively overweight, the serum will always appear mildly lipemic. Liver or pancreatic disorders can cause lipemia.