⚠️ Educational only. LabPlain does not provide medical advice or diagnosis. Always discuss your specific results with your healthcare provider.
What this test measures
Bilirubin is a yellow-orange substance created when your body breaks down old red blood cells. Your liver processes bilirubin and removes it through bile, which eventually leaves the body in stool.
A bilirubin blood test helps doctors evaluate how well your liver and bile ducts are working. It’s commonly included in a comprehensive metabolic panel (CMP) or liver function panel.
If bilirubin builds up in the bloodstream, it can cause jaundice — yellowing of the skin and eyes. Doctors use bilirubin testing to help investigate liver disease, bile duct blockage, gallstones, hepatitis, anemia, and other conditions affecting red blood cell breakdown or liver function.
Normal reference range
Total bilirubin: 0.1–1.2 mg/dL | Direct bilirubin: 0.0–0.3 mg/dL
Bilirubin is usually reported as total bilirubin, which includes both direct (conjugated) and indirect (unconjugated) bilirubin. Some labs break these values out separately because different patterns can point to different causes.
Reference ranges vary slightly between laboratories. Always compare your result to the range printed on your own lab report.
🩸 Why fasting sometimes matters
Fasting, dehydration, strenuous exercise, and certain medications can temporarily affect bilirubin levels. Mild elevations are sometimes harmless — especially in people with Gilbert syndrome, a common inherited condition that causes slightly higher bilirubin during stress or fasting.
What your result might indicate
↑ If High
High bilirubin may point to liver disease, hepatitis, bile duct blockage, gallstones, excessive red blood cell breakdown, or inherited conditions like Gilbert syndrome. Mild elevations are common and not always dangerous.
↓ If Low
Low bilirubin is usually not medically significant and rarely causes symptoms. Doctors generally focus more on elevated bilirubin than low values.
Symptoms associated with abnormal bilirubin
↑ High Bilirubin Symptoms
Yellowing of the skin or eyes (jaundice)
Dark urine
Pale or clay-colored stool
Fatigue or weakness
Nausea or vomiting
Abdominal pain, especially upper right side
Itchy skin
Loss of appetite
↓ Low Bilirubin Symptoms
Usually no noticeable symptoms
Typically not considered harmful
Rarely investigated on its own
Often considered a normal variation
May fluctuate naturally over time
Usually unrelated to liver disease
Often ignored unless other tests are abnormal
Doctors focus more on elevated levels
Common causes of abnormal bilirubin
What can raise bilirubin?
The most common causes of elevated bilirubin include liver inflammation (hepatitis), gallstones, bile duct obstruction, heavy alcohol use, cirrhosis, and conditions that increase red blood cell breakdown such as hemolytic anemia.
Some people naturally have mildly elevated bilirubin because of Gilbert syndrome — a common and usually harmless inherited condition where the liver processes bilirubin more slowly. Stress, illness, fasting, dehydration, and lack of sleep can temporarily increase bilirubin in these individuals.
What can lower bilirubin?
Low bilirubin is generally not considered clinically important. Some studies suggest it may occur with certain medications, caffeine use, or normal biological variation, but doctors rarely investigate isolated low bilirubin unless other lab results are abnormal.
Tests often ordered alongside bilirubin
Bilirubin is usually interpreted together with other liver and blood tests, including:
ALT (Alanine Aminotransferase) — evaluates liver cell damage
AST (Aspartate Aminotransferase) — another marker of liver inflammation
ALP (Alkaline Phosphatase) — helps detect bile duct blockage
GGT (Gamma-Glutamyl Transferase) — often elevated with bile duct problems or alcohol-related liver disease
CBC (Complete Blood Count) — checks for anemia or abnormal red blood cell breakdown
What to do next
A mildly abnormal bilirubin result does not automatically mean serious liver disease. Your doctor will interpret the result alongside your symptoms, medical history, medications, alcohol use, and other liver tests. Many bilirubin elevations are temporary or harmless, but significant or persistent abnormalities may require further evaluation or imaging.
Questions to ask your doctor
01Is my bilirubin elevation mild or something that needs further testing?
02Were my direct and indirect bilirubin levels both elevated?
03Could medications, fasting, or dehydration have affected this result?
04Do my other liver tests suggest liver inflammation or bile duct problems?
05Could this be Gilbert syndrome or another inherited condition?
06Do I need imaging tests like an ultrasound or CT scan?
Frequently asked questions
Does high bilirubin always mean liver disease?
No. Elevated bilirubin can happen for many reasons, including dehydration, fasting, temporary illness, or Gilbert syndrome — a common inherited condition that is usually harmless. Your doctor looks at the full pattern of liver tests before making conclusions.
What is jaundice?
Jaundice is yellowing of the skin and eyes caused by excess bilirubin in the bloodstream. It can occur with liver disease, bile duct blockage, hepatitis, gallstones, or increased red blood cell breakdown.
Can alcohol raise bilirubin?
Yes. Heavy alcohol use can inflame and damage the liver, making it harder for the body to process bilirubin normally. Alcohol-related liver disease often affects bilirubin along with ALT, AST, and GGT levels.
What is Gilbert syndrome?
Gilbert syndrome is a common inherited condition where the liver processes bilirubin more slowly than average. It often causes mild bilirubin elevations during stress, fasting, illness, or dehydration but is generally harmless and does not usually require treatment.
Can dehydration affect bilirubin levels?
Yes. Dehydration and fasting can temporarily raise bilirubin levels, especially in people with Gilbert syndrome. Drinking fluids and returning to a normal eating pattern may help levels normalize.