Bilirubin: Role in the Body, Types, Norms, and Deviations

Bilirubin is a bile pigment formed during the breakdown of hemoglobin from old red blood cells. It exists as indirect (unconjugated) and direct (conjugated) bilirubin, and their sum is the total bilirubin.

1. Types of Bilirubin and Their Role

Parameter	Characteristics
Indirect Bilirubin	Insoluble in water, toxic. Transported to the liver bound to albuminOne of the main proteins of the human body, responsible for maintaining normal blood composition and transporting various substances throughout the body. It also serves as a reserve source of amino acids. Albumins perform two very important functions: managing the distribution of water within the body, helping the blood transport vitamins, minerals, and medications. They are responsible for water exchange — they help retain it in the vessels and prevent it from excessively moving into the tissues (thus preventing the development of edema). Albumins influence the formation of tissue fluid, urine, and lymph, and also control the process of water absorption from the intestines..
Direct Bilirubin	Formed in the liver after conjugation with glucuronic acid. Excreted in bile.
Total Bilirubin	The sum of direct and indirect bilirubin.

Functions of Bilirubin:

Heme Utilization (from destroyed red blood cells).
Bile Component – aids in fat digestion.
Antioxidant – protects cells from damage.

2. Normal Bilirubin Levels in Blood

Type of Bilirubin	Normal Range (Adults)
Total	3.4–20.5 µmol/L
Direct	0–5.1 µmol/L (≤25% of total)
Indirect	<19 µmol/L

Note: In newborns, bilirubin can temporarily rise to 200–250 µmol/L (physiological jaundice).

3. Elevated Bilirubin: Causes and Symptoms

A. Hyperbilirubinemia with Predominant Indirect Bilirubin

Causes:

Hemolytic Anemia – accelerated destruction of red blood cells (autoimmune diseases, malaria).
Gilbert’s Syndrome – hereditary defect of the liver enzymeEnzymes are proteins that accelerate chemical reactions in the body. They ensure the occurrence of metabolic processes such as food digestion, energy release, cell formation, and many others. (UDP-glucuronosyltransferase).
Rh Incompatibility in Newborns.

Symptoms:

Jaundice (yellow skin and sclera).
Dark Urine (due to urobilin).
Fatigue, pallor (in anemia).

B. Hyperbilirubinemia with Predominant Direct Bilirubin

Causes:

Obstructive Jaundice – blockage of the bile ducts (gallstones, tumors).
Hepatitis (viral, alcoholic) – damage to liver cells.
Liver Cirrhosis.

Symptoms:

Jaundice with a greenish tint.
Skin Itching (due to accumulation of bile acids).
Light-Colored Stool, Dark Urine.

4. Decreased Bilirubin

Rare and usually not clinically significant.
Possible causes:

Use of certain medications (phenobarbital, vitamin C).
Hypothyroidism.

Symptoms:
Absent, but may correlate with a low level of antioxidant protection.

5. Diagnostics and Treatment

Tests:

Blood Chemistry (total, direct/indirect bilirubin).
Additional tests:

Liver function tests (ALT, AST, ALP).
Ultrasound of the liver and biliary tract.
Gilbert’s syndrome test (fasting + bilirubin analysis).

Treatment:

For hemolysis – address the cause (e.g., immunosuppressants for autoimmune anemia).
For liver diseases – hepatoprotectors, diet (table No. 5).
For obstructive jaundice – surgical removal of the obstruction (stone, tumor).
Gilbert’s Syndrome – usually requires no treatment, but fasting and alcohol should be avoided.

Examples of Pathologies by Bilirubin Levels

Ratio	Diagnosis
Indirect ↑, Direct normal	Hemolysis, Gilbert’s syndrome
Direct ↑, Indirect normal	Hepatitis, gallstone disease
Both ↑	Severe liver damage

Important: Jaundice is not always liver disease! Clarify the type of bilirubin for accurate diagnosis.