What is indirect bilirubin?

Indirect bilirubin is a chemical compound formed by the breakdown of heme. It is produced in the spleen and released into the bloodstream for circulation to the liver, where it is bound to albumin so it can be eliminated by the body, primarily in the feces. Abnormal levels of indirect bilirubin may be indicative of disease, and a doctor may order a blood test to check bilirubin levels if there is concern about an ongoing medical problem, especially jaundice, where the skin and eyes turn yellow.

When heme is broken down, the orange-yellow pigment bilirubin is one of the byproducts. Indirect bilirubin is not soluble in water, although it is soluble in fat. The spleen sends the pigment to the liver, where it is conjugated with albumin to make it water-soluble. At this point, it is known as direct or conjugated bilirubin. High levels of direct bilirubin in the body can cause jaundice and indicate that a duct in the liver is blocked or that a patient is experiencing another medical problem. Anemia and transfusion reactions can cause an elevation of indirect bilirubin.

Laboratories determine indirect bilirubin levels by measuring total bilirubin and then subtracting direct bilirubin to see how much is left. In healthy individuals, total bilirubin ranges from .3 to 1.9 milligrams per decaliter (mg/dL). Direct bilirubin is usually less than 0.3 mg/dL. Levels higher than this can cause jaundice and other problems, and are signs that something is wrong with the way the body processes heme and bilirubin. It is important to determine what is going on with the use of additional tests, medical imaging studies, and other diagnostic options.

When people take a bilirubin test, they're usually asked to fast for at least four hours before the test, and they may need to temporarily stop taking certain medications. A doctor can provide specific instructions for a patient. The test involves a small blood draw. Results are usually returned very quickly, especially if a doctor's office has a lab, and once the test results come back, people can discuss additional tests as well as treatment options to address the increase in blood levels. bilirubin.

Patients may want to know that results may vary between laboratories. If a test is unusually high and a patient appears healthy, a repeat test may be ordered to see if the results were a fluke. Not following instructions when preparing for the test can also result in a biased lab result.

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