- Bilirubin reference values
- When to take the bilirubin test
- What can be high bilirubin
- Increased indirect bilirubin
- Increased direct bilirubin
The bilirubin test helps to diagnose liver problems, bile ducts or hemolytic anemia, for example, since bilirubin is a product of the destruction of red blood cells and to be eliminated by the body it needs to be conjugated to a sugar in the liver and undergo the action of bile.
There are two main types of bilirubin that can be measured with this test:
- Indirect or unconjugated bilirubin: it is the substance that is formed at the time of the destruction of red blood cells in the blood and that is then transported to the liver. For this reason, its concentration is higher in the blood and may be altered when there is a condition involving red blood cells, such as hemolytic anemia, for example; Direct or conjugated bilirubin: corresponds to the conjugation between bilirubin and glucuronic acid, a sugar, in the liver. Direct bilirubin undergoes the action of bile in the intestine, being eliminated in the form of urobilinogen or sterobilobilinogen. Thus, the concentration of direct bilirubin is altered when there is a liver injury or biliary obstruction.
Bilirubin testing is requested with the aim of assessing liver function, monitoring the treatment of jaundiced newborns and assessing diseases that may interfere with bilirubin production, storage, metabolism or excretion. Normally the doctor orders total bilirubin, however laboratories also usually release direct and indirect bilirubin dosages, since these two dosages are responsible for the total bilirubin value. See what other tests help to identify liver problems.
The bilirubin test does not require preparation and is performed with a small amount of blood. However, the result of this examination may suffer interference when the sample is hemolyzed, that is, when the amount of destroyed red blood cells is very large, which usually happens when the collection is not performed correctly. That is why it is important that the collection is done in a reliable laboratory and with trained professionals.
Bilirubin reference values
The reference values for bilirubin in the blood are:
| Bilirubin type | Normal value |
| Direct Bilirubin | up to 0.3 mg / dL |
| Indirect bilirubin | up to 0.8 mg / dL |
| Total bilirubin | up to 1.2 mg / dL |
Some newborns may have very high levels of bilirubin, which may be due to the immaturity of the organs related to bilirubin metabolism or labor stress. The reference values for bilirubin in babies vary according to their lifetime, being:
- Up to 24 hours after birth: 1.4 - 8.7 mg / dL; Up to 48 hours after birth: 3.4 - 11.5 mg / dL; Between 3 and 5 days after birth: 1.5 - 12 mg / dL.
After the 6th day, the reference values are the same as those for the adult. Values above the reference value indicate that the baby has jaundice, which is one of the most frequent diseases in the newborn and that can be easily treated by means of phototherapy, which aims to decrease the bilirubin concentration in the baby's body. Learn more about neonatal jaundice, causes and how treatment is done.
When to take the bilirubin test
The bilirubin test is usually ordered by the doctor when there are symptoms of liver problems, such as excessive tiredness, frequent nausea, vomiting, constant pain in the belly, dark urine or yellowish skin, for example.
However, this test can also be used when cirrhosis, hepatitis and hemolytic anemia are suspected, for example, which causes signs such as pallor, frequent sleep, dry skin, hair loss or weak nails. See other symptoms of hemolytic anemia.
The decrease in bilirubin levels is usually due to the use of some medications, however, the elevated bilirubin levels usually indicate health problems that can be serious if left untreated.
What can be high bilirubin
The cause of the increase in bilirubin in the blood varies according to the type of bilirubin that is increased:
Increased indirect bilirubin
In these cases, the change in bilirubin levels is almost always caused by a change in the blood, however, the main causes include:
- Hemolytic anemia; Pernicious anemia; Hemoglobinopathies; Blood transfusions.
In addition, there are also cases where indirect bilirubin is increased due to a syndrome, known as Gilbert's syndrome, in which there is a genetic alteration that prevents the liver from properly eliminating bilirubin. Learn more about Gilbert's syndrome.
Increased direct bilirubin
When there is an increase in direct bilirubin it is usually a sign that there is a problem in the liver or bile ducts. Thus, some of the main causes include:
- Viral hepatitis; Alcoholic liver disease; Stone in the bile ducts; Tumors in the liver or bile ducts.
Excessive use of drugs that affect the liver, such as Paracetamol, can also lead to an increase in this type of bilirubin in the blood. Understand better what causes increased bilirubin and jaundice in adults.
