Total bilirubin test: normal range explained

Bilirubin is a yellowish substance left over when the body breaks down old red blood cells. The liver processes it into bile, which helps digest food, and a healthy liver removes most of it through the bile ducts into the stool.

Total bilirubin counts both forms together: the direct (conjugated) bilirubin the liver has already processed, and the indirect (unconjugated) bilirubin that has not yet been processed. Reports often print direct bilirubin beside it and calculate indirect bilirubin as the difference.

Doctors order bilirubin to check liver health, to find the cause of jaundice (yellow skin and eyes), to look for a blocked bile duct, to monitor known liver disease and to see whether a treatment is working. It is a standard part of a liver function test and the comprehensive metabolic panel.

Symptoms that prompt the test include jaundice, dark urine, pale or clay-coloured stool and stomach pain. Newborns are commonly tested because jaundice in the first days of life is usual and the level is watched.

Bilirubin can rise or fall for reasons a doctor sorts out with the rest of the liver panel and your history.

• Many medicines can change bilirubin; antibiotics, birth control pills, sleeping pills and seizure medicines are linked with lower values. Do not stop a medicine unless your doctor tells you to.
• Certain foods and strenuous exercise can also raise the level.
• A sample in which red blood cells have broken (haemolysed) may be rejected by the lab, which then asks for a fresh draw.
• Gilbert syndrome, a common and harmless inherited trait, raises indirect bilirubin mildly and is often found by chance on a routine test.
• Faster breakdown of red blood cells (haemolytic anaemia), liver disease and a blocked bile duct are the three groups of causes doctors consider for a high value.
• Newborns normally run higher in the first days of life, and labs print their own ranges.