Bilirubin, Total

Overview

Total bilirubin is a blood biomarker that measures the combined amount of bilirubin in the bloodstream, including both conjugated (direct) and unconjugated (indirect) forms. Bilirubin is a yellowish substance produced during the normal breakdown of old red blood cells. The liver processes bilirubin and excretes it in bile to aid digestion. Measuring total bilirubin helps assess liver function and detect liver diseases or bile duct obstructions. It is also crucial in diagnosing and monitoring jaundice, especially in newborns, where elevated bilirubin can cause serious complications if untreated¹³.

Scientific Background

Bilirubin is formed from the breakdown of heme, a component of hemoglobin in red blood cells. When red blood cells are degraded, heme is converted to biliverdin and then reduced to unconjugated bilirubin, which is lipid-soluble and transported to the liver bound to albumin. In the liver, bilirubin undergoes conjugation with glucuronic acid, making it water-soluble (conjugated bilirubin) and allowing excretion into bile. In the intestines, bilirubin is further metabolized to urobilinogen and stercobilin, which give feces their brown color. Some urobilinogen is reabsorbed and excreted in urine, giving it a yellow color. The balance between unconjugated and conjugated bilirubin, and their total, reflects liver metabolic capacity and biliary excretion efficiency²¹.

Measurement and Testing

Total bilirubin is commonly measured via a blood test using serum or plasma samples. The test quantifies both direct (conjugated) and indirect (unconjugated) bilirubin. Factors affecting results include hemolysis, fasting status, and certain medications. Testing is recommended when symptoms of liver dysfunction or jaundice appear, or for routine monitoring in liver disease or newborn screening. Urine bilirubin testing may complement blood tests but is less specific³⁴.

Reference Ranges

Standard reference ranges for total bilirubin in adults typically fall between 0.1 to 1.2 mg/dL (1.71 to 20.5 µmol/L). These ranges may vary slightly by laboratory and measurement method. Newborns often have higher bilirubin levels shortly after birth due to immature liver function, with levels monitored carefully to prevent toxicity. Age, sex, and ethnicity can influence baseline bilirubin levels, but significant deviations usually indicate pathology. Interpretation must consider clinical context and other liver function tests⁴¹.

High Values

Elevated total bilirubin (hyperbilirubinemia) can result from increased red blood cell breakdown (hemolysis), liver dysfunction (hepatitis, cirrhosis), or bile duct obstruction (gallstones, tumors). High bilirubin causes jaundice, characterized by yellowing of the skin and eyes, dark urine, and pale stools. Severe elevations may indicate serious liver disease or biliary obstruction requiring urgent evaluation. In newborns, very high bilirubin can cause kernicterus, a form of brain damage¹³.

Low Values

Low total bilirubin levels are uncommon and generally not clinically significant. They may occur in conditions with reduced red blood cell turnover or in some rare metabolic disorders. Since bilirubin is a breakdown product, very low levels do not typically indicate disease but should be interpreted in the broader clinical context¹.

Improving Biomarker Levels

To maintain healthy bilirubin levels, addressing underlying causes is essential. Lifestyle modifications include avoiding excessive alcohol, managing medications that affect liver function, and preventing liver infections. In cases of hemolysis, treating the cause reduces bilirubin production. For newborn jaundice, phototherapy is effective by converting bilirubin to more soluble forms for excretion. Supplements are not typically used to alter bilirubin but supporting liver health with antioxidants and avoiding hepatotoxins can be beneficial²¹.

Importance of Tracking

Monitoring total bilirubin is vital for early detection of liver dysfunction, hemolytic disorders, and bile duct obstructions. Regular tracking guides treatment decisions, assesses disease progression, and helps prevent complications such as jaundice and neurological damage in infants. It is a key component of liver function panels and newborn screening protocols³¹.

Disclaimer

The information provided in this document is for educational purposes only and does not constitute medical advice. It is essential to consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.