What Is a Bilirubin Blood Test?
Bilirubin is a yellow pigment that is in everyone’s blood and stool. If you notice a yellowing of your skin or the whites of your eyes, this is called jaundice, and it may be caused by high levels of bilirubin.
Bilirubin is made in the body when old red blood cells are broken down. The breakdown of old cells is a normal, healthy process. After circulating in your blood, bilirubin then travels to your liver. In the liver, bilirubin is excreted into the bile duct and stored in your gall bladder. Eventually, the bilirubin is released the small intestine as bile to help digest fats and ultimately excreted with your stool.
Bilirubin attached to sugar is called “direct” or “conjugated” bilirubin, and bilirubin without sugar is called “indirect” or “unconjugated” bilirubin. All the bilirubin in your blood together is called “total” bilirubin.
A bilirubin blood test will get an accurate count of all three bilirubin levels in your blood: direct, indirect, and total.
Common Reasons to Test for Bilirubin
If bilirubin is not being attached to sugars (conjugated) in the liver and/or is not being adequately removed from the blood, it can mean that there is damage to your liver. Testing for bilirubin in the blood is therefore a good test of damage to your liver.
Newborn infants often have some jaundice, and bilirubin in the blood may be tested several times in the first few days of an infant’s life to check that the liver is starting to work properly. Jaundice in a newborn can be very serious if left untreated.
Other reasons for high bilirubin levels could be that more blood cells are being destroyed than normal. This is called hemolysis.
Sometimes bilirubin is measured as part of a “panel” of tests. Often, the liver is evaluated with a group of tests that include bilirubin, alanine transaminase (ALT), asparate transaminase (AST), alkaline phosphatase (ALP), albumin, total protein, and others.
How Is the Bilirubin Blood Test Performed?
A small amount of your blood is needed to perform this test. The blood sample is obtained through venipuncture, where a needle is inserted into a vein through the skin in your arm or hand, and a small amount of blood comes out through the needle into tubing and is stored in a test tube.
How Do I Prepare for the Bilirubin Blood Test?
For this test, you will need to fast (not eat or drink anything other than water) for four hours before you have the test performed. Drink a normal amount of water before going to the laboratory or collection site.
You may have to stop taking certain medications before the test is performed, but only if your doctor tells you to do this. Examples of drugs that can affect bilirubin levels include antibiotics like penicillin G, sedatives like phenobarbital, diuretics like furosemide, and asthma medications like theophylline. However, there are many drugs that can influence bilirubin levels. Talk to your doctor before your test to see if you should stop or continue taking medication.
What Are the Risks of the Bilirubin Blood Test?
When the blood is collected, you may feel some moderate pain or a mild pinching sensation, though this is usually very short in duration and very slight. After the needle is taken out, you may feel a throbbing sensation, and you will be instructed to apply pressure to the site where the needle entered your skin. A bandage will be applied that needs to remain in place typically for 10 to 20 minutes, and you should avoid using that arm for heavy lifting for the rest of the day.
There are some very rare risks to taking a blood sample:
- lightheadedness or fainting
- hematoma—a bruise where blood accumulates under the skin
- infection—usually prevented by the skin being cleaned before the needle is inserted
- excessive bleeding—Bleeding for a long period afterward may indicate a more serious bleeding condition and should be reported to your doctor.
What Is a Normal Result for the Bilirubin Blood Test?
In an older child or adult, normal values of direct (conjugated) bilirubin are from 0 to 0.3 milligrams per deciliter (mg/dL). Normal values of total bilirubin (direct and indirect) are from 0.3 to 1.9 mg/dL.
In a newborn, higher bilirubin is normal due to the stress of birth. Normal bilirubin in a newborn would be under 5 mg/dL, but up to 60 percent of newborns have some kind of jaundice and bilirubin levels above 5 mg/dL.
What Is an Abnormal Result for the Bilirubin Blood Test?
Your doctor may want to perform further blood tests or an ultrasound if high levels of bilirubin are detected in your blood. In an adult, high bilirubin may be due to problems with the liver, bile ducts, or gallbladder. Examples include:
- drug toxicity
- liver diseases like hepatitis
- Gilbert’s disease (a genetic disease affecting some families)
- cirrhosis (scarring of the liver)
- biliary stricture (part of the bile duct is too narrow to allow fluid to pass)
- cancer of the gallbladder or pancreas
Another cause of high bilirubin may be due to problems in the blood instead of problems in the liver. Blood cells breaking down too fast can be caused by: hemolytic anemia (too many blood cells being destroyed from an autoimmune disease, genetic defect, drug toxicity, or infection); or transfusion reaction (your immune system can attack some blood given during a transfusion).
In an infant, high bilirubin and jaundice can be very dangerous, and may be caused by several factors. There are three common types:
- physiological jaundice (at 2-4 days after birth, caused by a brief delay in the functioning of the liver, usually not serious)
- breast feeding jaundice (during first week of life, caused by a baby not nursing well or low milk supply in the mother)
- breast milk jaundice (after 2-3 weeks of life, caused by the processing of some substances in breast milk)
All of these can be easily treated and are usually harmless if treated. Some more serious conditions that cause high bilirubin and jaundice in the infant:
- abnormal blood cell shapes (like sickle cell anemia)
- blood type mismatch between infant and mother (called erythroblastosis fetalis)
- lack of certain important proteins due to genetic defects
- bleeding in the scalp due to a difficult delivery
- high levels of red blood cells due to small size, prematurity
In both adults and children, symptoms related to high bilirubin involve jaundice, a yellowing of the skin or eyes, fatigue, itchy skin, dark urine, and low appetite.