What Is a Bilirubin Test?
Bilirubin is an orange-yellow pigment that occurs normally when part of your red blood cells break down. Your liver takes the bilirubin from your blood and changes its chemical makeup so that most of it is passed through your poop as bile.
If your bilirubin levels are higher than normal, it's a sign that either your red blood cells are breaking down at an unusual rate or that your liver isn't breaking down waste properly and clearing the bilirubin from your blood.
Another option is that there's a problem somewhere along the pathway that gets the bilirubin out of your liver and into your stool.
Why Do You Get the Bilirubin Test?
High bilirubin levels are common in newborns. Doctors use the age of the newborn and the bilirubin type and levels to determine if treatment is necessary.
What Happens During a Bilirubin Test?
Bilirubin levels can be measured in your urine and blood. Most standard urine tests routinely check for bilirubin. If the urine is positive for bilirubin in a standard urine test, your doctor will order further testing to measure levels present in your blood.
Most often, bilirubin tests are done by blood tests. A nurse or lab technician will draw blood through a small needle inserted into a vein in your arm. The blood is collected in a tube. With newborns, blood is usually drawn by using a needle to break the skin of the heel.
Your doctor will send the blood to a lab for analysis.
Before the test, tell your doctor about how active you've been and what food and medicines you've taken. Certain medications may alter your results. After the test, you'll be able to continue with your normal activities right away.
Another noninvasive bilirubin test is called a transcutaneous bilirubin measurement. This test is particularly helpful for squirmy babies or young children or anyone averse to needle pokes. The doctor will place a device against your chest or head. The device will send a quick light flash through your skin to measure your bilirubin levels.
Who Should Get a Bilirubin Test?
Your doctor may order a bilirubin test if you:
- Show signs of jaundice
- Have anemia, or low red blood cells
- Might be having a toxic reaction to drugs
- Have a history of heavy drinking
- Have been exposed to hepatitis viruses
- Have cirrhosis
You might also have your bilirubin tested if you have symptoms like:
How Do You Prepare for the Bilirubin Test?
You should avoid eating or drinking for 4 hours before the test. Your doctor may also instruct you to stop taking certain medicines before the test because they may interfere with the results.
Drugs that can increase bilirubin levels in your blood include some antibiotics, antimalarials, monoamine oxidase (MAO) inhibitors, morphine, oral contraceptives, and some steroids, among others.
Drugs that can lower bilirubin levels in your blood may include barbiturates, caffeine, penicillin, and high-dose salicylates.
What Do the Results Mean?
A bilirubin test measures total bilirubin. It can also give levels of two types of bilirubin: unconjugated and conjugated.
Unconjugated ("indirect") bilirubin. This is the bilirubin created from red blood cell breakdown. It travels in the blood to the liver.
Conjugated ("direct") bilirubin. This is the bilirubin once it reaches the liver and undergoes a chemical change. It moves to the intestines before being removed through your stool.
Normal bilirubin levels
For adults over 18 years, normal total bilirubin can be up to 1.2 milligrams per deciliter (mg/dl) of blood. For those under 18, the normal level will be will be 1 mg/dl. Normal results for conjugated (direct) bilirubin should be less than 0.3 mg/dl. Normal bilirubin levels in newborns can reach as high as 12 mg/dl.
Men tend to have slightly higher bilirubin levels than women. Black people tend to have lower bilirubin levels than people of other races.
High bilirubin levels
Bilirubin levels higher than 2.0 mg/dl is an indicator of jaundice in adults. For newborns, doctors will recommend treatment when bilirubin levels become higher than 15 mg/dl.
What causes high bilirubin?
In addition to jaundice, high total bilirubin levels in adults may also be caused by:
- A reaction to a blood transfusion
- Gilbert syndrome—a common, inherited condition in which there is a deficiency of an enzyme that helps break down bilirubin
- Viral hepatitis
- A reaction to drugs
- Alcoholic liver disease
Very strenuous exercise, such as marathon running, can raise your bilirubin levels.
In newborns, high bilirubin levels that don't level out in a few days to 2 weeks may be a sign of:
- Blood type incompatibility between mother and child
- Lack of oxygen
- An inherited infection
- A disease affecting the liver
What causes low bilirubin?
Lower than normal levels of bilirubin typically aren't a problem. Low levels of bilirubin (hypobilirubinemia) may be a result of certain medications or caffeine. Low levels of bilirubin may also be linked to some autoimmune diseases such as rheumatoid arthritis, lupus, polymyositis, and Sjogren's syndrome. It also may be an indicator for cardiovascular disease.
How Long Does it Take to Get Your Results?
Your blood sample will be sent to a lab to be processed. The sample is processed by a machine. It can take a few hours or a day to get the results of your blood bilirubin test.
Bilirubin is an orange-yellow pigment that occurs as a normal part of red cells breaking down in your body. Typically, your liver will take your bilirubin from your blood so it can be excreted from your body.
If your liver isn't working properly, your blood may have higher levels of bilirubin in it. This can point to signs of liver or bile duct diseases.
Bilirubin tests are blood tests given to newborns and adults who show signs of jaundice.
Common urine tests often also test for levels of bilirubin.