What is Bilirubin
Bilirubin is a yellowish substance. Bilirubin is made in the body when the hemoglobin protein in old red blood cells is broken down. The breakdown of old cells is a normal, healthy process. Bilirubin is found in bile, a fluid your liver makes that helps you digest food. Bilirubin is stored in the gallbladder and is involved in digesting food. Most bilirubin is eliminated in the feces or urine. Elevated bilirubin levels may indicate certain diseases. It is responsible for the yellow color of bruises and the yellow discoloration in jaundice. Its subsequent breakdown products, such as stercobilin, cause the brown color of feces. A different breakdown product, urobilin, is the main component of the straw-yellow color in urine. If your liver is healthy, it will remove most of the bilirubin from your body. If your liver is damaged, bilirubin can leak out of your liver and into your blood. When too much bilirubin gets into the bloodstream, it can cause jaundice, a condition that causes your skin and eyes to turn yellow. Signs of jaundice, along with a bilirubin blood test, can help your health care provider find out if you have liver disease.
What is the bilirubin test used for?
The bilirubin test checks the health of your liver by measuring the amount of bilirubin in your blood or urine. This can help diagnose or monitor problems related to your liver or red blood cells when the bilirubin level is too high. After circulating in your blood, bilirubin then travels to your liver. In the liver, bilirubin is processed, mixed into bile, and then excreted into the bile ducts and stored in your gallbladder. Eventually, the bile is released into the small intestine to help digest fats. It’s ultimately excreted within your stool. Bilirubin attached by the liver to glucuronic acid, a glucose-derived acid, is called direct, or conjugated, bilirubin. Bilirubin not attached to glucuronic acid is called indirect, or unconjugated, bilirubin. All the bilirubin in your blood together is called total bilirubin. A comprehensive bilirubin blood test will get an accurate count of all three bilirubin levels in your blood: direct, indirect, and total.
Testing for bilirubin in the blood is a good way of testing for liver damage. Sometimes bilirubin is measured as part of a “panel” of tests. Often, the liver is evaluated with a group of tests that also include:
- Alanine transaminase
- Aspartate aminotransferase
- Alkaline phosphatase
- Total protein
What do bilirubin results mean?
Your test results will also include reference ranges, the normal range of bilirubin levels. Results that fall outside the reference range, especially those above the upper normal level, may indicate the presence of disease or a need for further testing.
In an older child or adult, normal values of direct bilirubin are from 0–0.4 milligrams per deciliter (mg/dL).
Normal values of total bilirubin are from 0 - 1.2 mg/dL.
Normal results can vary, but high bilirubin levels may mean your liver isn't working right. However, abnormal results don't always mean you have a medical condition that needs treatment. Other things may cause higher than normal bilirubin levels, such as certain medicines and foods or strenuous exercise.
Kalakonda A, Jenkins BA, John S. Physiology, Bilirubin. [Updated 2022 Sep 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK470290/
Joseph A, Samant H. Jaundice. [Updated 2023 Feb 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK544252/
Fevery J. Bilirubin in clinical practice: a review. Liver Int. 2008 May;28(5):592-605. doi: 10.1111/j.1478-3231.2008.01716.x. PMID: 18433389.
Maisels MJ, Conrad S. Transcutaneous bilirubin measurements in full-term infants. Pediatrics. 1982 Sep;70(3):464-7. PMID: 7110821.
American Academy of Pediatrics Subcommittee on Hyperbilirubinemia. Management of hyperbilirubinemia in the newborn infant 35 or more weeks of gestation. Pediatrics. 2004 Jul;114(1):297-316. doi: 10.1542/peds.114.1.297. Erratum in: Pediatrics. 2004 Oct;114(4):1138. PMID: 15231951.
A low level of total bilirubin in the blood is not a cause for concern. There are some medicines/supplements (like vitamin C) that can cause bilirubin levels to drop, but there are no detrimental effects associated with this.
When your body has too much bilirubin, your skin and the whites of your eyes will start to yellow. This condition is called jaundice. In both adults and children, symptoms related to high bilirubin can involve jaundice, a yellowing of the skin or eyes, fatigue, itchy skin, dark urine, and low appetite. Another reason for high bilirubin levels could be that more red blood cells are being destroyed than normal. This is called hemolysis.
High bilirubin levels are usually a sign that something is not working as expected in your liver or gallbladder. Some of these conditions aren’t too serious, but it’s important to monitor and treat them.
Anyone with jaundice, which is the main sign of high bilirubin levels, should contact their doctor. If your doctor isn’t immediately sure what’s causing your high bilirubin levels, you may need to return for additional blood, liver function, or other tests.
Causes of abnormal results:
Your doctor may want to perform further blood tests or an ultrasound if high levels of bilirubin are detected in your blood. In an adult, high bilirubin may be due to problems with the liver, bile ducts, or gallbladder. Examples include:
- Liver diseases, like hepatitis
- Gilbert’s syndrome, a genetic disease
- Cirrhosis, which is scarring of the liver
- Biliary stricture, where part of the bile duct is too narrow to allow fluid to pass
- Cancer of the gallbladder or pancreas
- Drug toxicity
High bilirubin may also be due to problems in the blood instead of problems in the liver.
Blood cells breaking down too fast can be caused by:
Hemolytic anemia: This occurs when too many blood cells are being destroyed from an autoimmune disease, genetic defect, drug toxicity, or infection, and the liver is unable to metabolize the amount of indirect bilirubin in the body.
Transfusion reaction: This occurs when your immune system attacks blood that was given to you through a transfusion.
Infant jaundice: In an infant, high (usually indirect) bilirubin and jaundice can be very dangerous and may be caused by several factors. There are three common types:
Physiological jaundice: at two to four days after birth, caused by a brief delay in the functioning of the liver and usually not serious
Breastfeeding jaundice: during the first week of life, caused by a baby not nursing well or low milk supply in the mother
Breast milk jaundice: after two to three weeks of life, caused by the processing of some substances in breast milk
→ All of these can be easily treated and are usually harmless if treated.
Some more serious conditions that cause high bilirubin and jaundice in an infant include:
- abnormal blood cell shapes, such as sickle cell anemia
- blood-type mismatch between infant and mother, leading to severe breakdown of the baby’s red blood cells, called erythroblastosis fetalis
- lack of certain important proteins due to genetic defects
- bruising due to a difficult delivery
- high levels of red blood cells due to small size, prematurity
Additional note: Infants commonly have higher bilirubin levels in the blood after birth as their livers continue to develop. As such, bilirubin testing is standard for all infants in their first 48 hours and is also often performed as a precautionary measure to monitor the change in these levels. If you are concerned about your baby’s bilirubin levels or if they are showing signs of jaundice, it is important to talk with your pediatrician.
More on Jaundice:
Elevated bilirubin levels (>2.5-3 mg/dL) cause jaundice and can be classified into different anatomical sites of pathology:
- prehepatic (increased bilirubin production),
- hepatic (liver dysfunction),
- or posthepatic (duct obstruction).
Another way of approaching hyperbilirubinemia is to divide it into two general categories:
- unconjugated hyperbilirubinemia and
- conjugated hyperbilirubinemia.
The prevalence of hyperbilirubinemia varies depending on the cause:
Conjugated hyperbilirubinemia is common in individuals with hepatocellular injuries and biliary obstruction and is also common in persons with sepsis. Some of the inherited diseases associated with conjugated hyperbilirubinemia are estimated to affect 4%-13% of the US population, while Dubin-Johnson syndrome (DJS) is rare except in Iranian Jews, in whom the prevalence is about 1 in 1300.
Unconjugated hyperbilirubinemia is common in newborns and is likely related to a higher hematocrit (50%-60%) with increased cell turnover (the average lifespan of a red cell is about 85 days in the neonate) combined with decreased uridine diphosphoglucuronic glucuronosyltransferase (UGT) activity. One study found that up to 6.1% of neonates had unconjugated bilirubin levels higher than 12.9 mg/dL. Breastfeeding was more common in neonates with higher levels of unconjugated hyperbilirubin.
How can high bilirubin be treated?
In adults, treatment for high bilirubin levels depends on the underlying cause. Treatment can include approaches such as stopping the use of a toxic drug, surgery, or long-term therapy.
These are a few treatment approaches:
- If high bilirubin levels are caused by drugs, a change of medication can resolve the effects.
- In cases of obstructive hyperbilirubinemia, surgery (usually laparoscopic) may be needed to remove gallstones or other sources of obstruction.
- Severe liver or pancreatic diseases would require the care of a qualified hepatologist, with treatment options ranging from drug therapies to organ transplants.
- Sometimes, hyperbilirubinemia may not require specific treatment. For example, symptoms of acute viral hepatitis typically go away on their own as the infection resolves. The same applies to Gilbert's syndrome, which is not considered harmful and does not require treatment.
If you are experiencing any symptoms of liver impairment, speak with your healthcare provider before taking any medications.
While there are no home treatments that bring bilirubin levels down, you can avoid placing additional stress on the liver by cutting out alcohol, red meat, processed foods, and refined sugar.
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