Difference between Direct and Indirect Bilirubin

The difference between direct and indirect bilirubin lies in the fact that direct bilirubin is the type of bilirubin the human body can easily remove. It is similar to waste that the body can easily handle and eliminate, but indirect bilirubin is bilirubin combined with a protein in the bloodstream. It makes it tough for the body to eliminate. It is comparable to bilirubin, which requires a specific host before getting out of the body. In this article, we will look into the differences between direct and indirect bilirubin.

What is Bilirubin?

Bilirubin is a yellow-coloured substance that is formed during the breakdown of old Red Blood Cells. It is primarily present in the liver. Bilirubin has a crucial role in cell protection. Bilirubin is an essential component of the body’s waste-elimination system. Excess bilirubin can induce jaundice, which is characterized by yellowing of the skin and eyes. Bilirubin is found in the liver in two forms mentioned below.

Direct Bilirubin

Direct bilirubin, also referred to as conjugated bilirubin, is a modified version of a chemical created when red blood cells are broken down. The enzyme glucuronyltransferase attaches glucuronic acid to bilirubin, making it less toxic and easier for the body to eliminate. Direct bilirubin dissolves in water.

The overall amount of bilirubin in our bodies comprises both direct and indirect forms. The bilirubin normal range in adults are:

Total Bilirubin Normal Range

The total bilirubin normal range is 0.1-1.2 mg/dL. But slightly higher levels are observed in newborns.

Direct Bilirubin Normal Range:

The direct bilirubin normal range falls between 0.0-0.3 mg/dL. A higher direct bilirubin level indicates an underlying issue with the liver, bile ducts. or gallbladder.

Causes of Direct Bilirubin Increase

Direct bilirubin increases due to liver diseases like hepatitis, cirrhosis, bile duct blockage, and excessive breakdown of Red Blood Cells etc. Some genetic diseases like Dubin-Johnson syndrome and Rotor syndrome can also cause increase in direct bilirubin.

Indirect Bilirubin

Indirect bilirubin, additionally referred to as unconjugated bilirubin, is produced directly by the breakdown of hemoglobin, a component of red blood cells. This kind of bilirubin binds to a protein called albumin, which helps carry it from the bloodstream to the liver. However, indirect bilirubin is extremely hazardous. So, in the liver, enzymes convert it into a less toxic version known as direct bilirubin.

Indirect bilirubin can dissolve in fat but not water. Several factors can cause bilirubin levels to increase, including Red blood cell breakdown also known as hemolytic anaemia, skin injuries may result in bleeding, lung haemorrhage, and genetic diseases.

Causes of Indirect Bilirubin Increase

Indirect bilirubin increases due to excessive Red Blood Cells breakdown, genetic conditions, liver cells not working right and neonatal jaundice. Few genetic disorders like Gilbert’s syndrome and Crigler-Najjar syndrome can also result in increased indirect bilirubin.

Levels of Bilirubin

The following are the levels of bilirubin:

• Direct Bilirubin: This is the quantity of bilirubin that has already been processed by the liver and is ready to be eliminated from the body. A normal direct bilirubin level is less than 0.3 mg/dL, or 5.1 µmol/L.

• Total Bilirubin: This comprises both direct and indirect bilirubin, which the liver has not yet digested. Normal total bilirubin levels vary from 0.1 to 1.2 mg/dL (1.71 to 20.5 µmol/L). Bilirubin is a chemical in your blood that is formed when old red blood cells break down. When doctors measure bilirubin levels, they look for two types: direct (or conjugated) and total bilirubin.

Abnormal Levels of Bilirubin

When bilirubin levels are abnormally high, it can indicate a health concern that requires medical treatment. However, low bilirubin levels are usually not a cause for concern.

• Hyperbilirubinemia occurs when bilirubin levels in the blood are extremely high. Blood cell breakdown, genetic disorders, and specific drugs can all contribute to this phenomenon. High bilirubin levels can damage the brain and cause seizures.
• High bilirubin levels can also cause jaundice, which is characterised by yellowing of the skin, eyes, and mouth. Gallstones, tumours, and hepatitis are some of the possible causes.

Difference Between Direct and Indirect Bilirubin

The direct vs indirect bilirubin in a tabulated form is given below:

Parameters	Direct Bilirubin	Indirect Bilirubin
Description	It is a modified form of bilirubin produced when the body breaks down hemoglobin.	The body produces indirect bilirubin when it breaks down hemoglobin.
	Direct bilirubin is also called Conjugated bilirubin.	Indirect bilirubin is also called Unconjugated bilirubin.
Transporter	Direct bilirubin does not need a protein carrier for transportation.	It moves from the bloodstream to the liver via attaching to albumin.
Solubility	It is soluble in water and can be released in the bile.	It is not soluble in water and cannot be released in the bile.
	The liver converts bilirubin into direct bilirubin.	Indirect bilirubin is generated when red blood cells break down.
Normal Range	The normal range is normally between 0.0 and 0.3 mg/dL.	The normal range is normally between 0.2 to 0.8 mg/dL.
Side effects	Elevated levels may indicate liver injury or occlusion of the bile ducts.	Elevated levels may indicate hemolytic anaemia or other disorders that induce excessive destruction of red blood cells.

Conclusion – Direct and Indirect Bilirubin

To conclude, the difference between direct bilirubin and indirect bilirubin is discusses above. The direct bilirubin is a water-soluble type of bilirubin that the body can reject more easily. It is mostly prevalent in bile and plays an important function in waste elimination. On the other hand, indirect bilirubin is the first byproduct of haemoglobin breakdown. It attaches to proteins in the blood and travels to the liver for further processing. Indirect bilirubin is lipid-soluble and can be harmful in high concentrations. Both types are necessary for understanding liver function and diagnosing specific medical disorders.

FAQs on Difference between Direct and Indirect Bilirubin

What is the Difference Between Direct Bilirubin and Total Bilirubin?

Total bilirubin is the sum of direct and indirect bilirubin, whereas direct bilirubin is conjugated bilirubin only.

Why is Direct Bilirubin Higher than Total Bilirubin?

Due to the presence of monoclonal immunoglobulins, the measurement of direct bilirubin is sometimes falsely recorded as being higher than total bilirubin.

Which Bilirubin causes Jaundice, Direct or Indirect?

Prehepatic causes of jaundice include hemolysis and hematoma resorption, which lead to elevated levels of unconjugated (indirect) bilirubin.

What Happens if Indirect Bilirubin is High?

High bilirubin leads to jaundice, a yellow cast to your skin and the whites of your eyes.

What Happens if Total Bilirubin is High?

High bilirubin leads to jaundice, a yellow cast to your skin and the whites of your eyes.

What does it Mean when Bilirubin Total and Direct are High?

Results that are higher may mean that you have a liver problem, hepatitis, or gallstones.