What is Bilirubin?

Bilirubin is a yellowish substance produced during the breakdown of old or damaged red blood cells in the liver. It plays a crucial role in the body's waste removal process and can serve as an indicator of liver function and overall health.

Why is Bilirubin Important?

Unconjugated (water-insoluble) bilirubin is bound to albumin, a protein that transports it from the bloodstream to the liver. The liver is responsible for processing unconjugated bilirubin into conjugated (water soluble) bilirubin, which is excreted into bile before leaving the body through urine and feces. The levels of bilirubin in the blood are an important indicator of liver function and health. High levels of bilirubin can indicate liver dysfunction or diseases such as hepatitis, cirrhosis, or bile duct obstruction. High levels of bilirubin in the blood can lead to jaundice, a condition characterized by yellowing of the skin and eyes. Jaundice can occur in newborns with immature liver function, in adults with liver disease, or in conditions that lead to an increased breakdown of red blood cells.

Measuring bilirubin levels is a common part of liver function tests. These tests can help diagnose and monitor liver diseases and conditions that affect bile ducts or the breakdown of red blood cells.

Understanding Your Bilirubin Test Results

Bilirubin levels are typically reported in milligrams per deciliter (mg/dL) of blood. SiPhox Health measures total bilirubin which includes both conjugated and unconjugated forms.

According to the American Board of Internal Medicine, a normal serum total bilirubin reference range is between 0.3-1.0 mg/dL. University of Rochester Medical Center states that adults with jaundice typically have levels above 2.5 mg/dL.

Interpreting Bilirubin Results:

Higher than normal bilirubin levels may indicate liver dysfunction, bile duct obstruction, hemolytic anemia, or other underlying health conditions. Elevated bilirubin levels, however, may be benign (harmless). According to a YouTube video by Dr. S. Miles, about 10% of the population may have Gilbert's syndrome which is a benign elevation in bilirubin. Some studies even indicate that elevated bilirubin may have cardioprotective effects which could be due to its anti-oxidative properties.

Lower than normal bilirubin levels are less common but may suggest certain medications, genetic disorders, or conditions affecting red blood cell production. Additional testing may be required to confirm the diagnosis. Cleveland Clinic states that low levels of bilirubin generally aren't a cause for concern.

It is important to talk to a doctor if you are concerned with any of your levels.

Maintaining a healthy liver is important for your overall health. The American Liver Foundation has 13 tips, including a healthy weight, balanced diet, regular exercise, avoiding toxins and illicit drugs, and limiting alcohol intake among others.

    Where Can I Learn More?

    YouTube - Bilirubin Metabolism: Unconjugated and Conjugated Bilirubin

    MedlinePlus - Bilirubin Blood Test

    American Liver Foundation (video) - Nutrition and Liver Health Webinar

    Scientific Literature:

    Creeden, Justin F et al. “Bilirubin as a metabolic hormone: the physiological relevance of low levels.” American journal of physiology. Endocrinology and metabolism vol. 320,2 (2021): E191-E207. doi:10.1152/ajpendo.00405.2020


    Flack, Kyle D et al. “Cutting edge concepts: Does bilirubin enhance exercise performance?.” Frontiers in sports and active living vol. 4 1040687. 11 Jan. 2023, doi:10.3389/fspor.2022.1040687

    Khadem Al-Hosseini, M et al. “The effect of vitamin C supplementation in the last month of pregnancy on neonatal bilirubin levels; A double-blind randomized clinical trial.” Complementary therapies in medicine vol. 50 (2020): 102359. doi:10.1016/j.ctim.2020.102359