| Material | serum or EDTA plasma or heparin plasma 0.5 ml |
| Method | photometry |
| Duration | 1 day |
| Remark | - The breakdown of haemoglobin and other cytochromes produces bilirubin. Its glucuronidation is intrahepatocellular (= direct bilirubin) and it is excreted through the intestines. Visible icterus correlates with concentrations of 17 µmol/l or more, except in horses (horse: > 75 µmol/l).
- Prehepatic icterus: excessive haemoglobin concentration causes increased levels of indirect bilirubin (= not glucuronidated).
- Intrahepatic icterus: damage of liver cells causes increase in both direct and indirect bilirubin.
- Posthepatic icterus (rare): increase in direct bilirubin caused by retention of bile.
- Cattle: Total bilirubin has a strong negative correlation with blood glucose levels and hence is a sensitive indicator for imbalances in the composition of food rations. Strong increase occurs due to microhaemolysis as part of septicaemia, e.g. in case of mastitis, endometritis or salmonellosis, and is prognostically unfavourable.
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