Bilirubin, Direct
The part of bilirubin your liver has already processed. A raised level can be a sign that bile isn't draining from the liver as usual.
AI-verified against cited sources. Awaiting expert reviewAlso called DBIL, D BILI, D BILLOINC 1968-7
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What it is
Bilirubin is a yellow pigment made when old red blood cells break down. The liver changes it so it can dissolve in water and leave the body in bile. This processed form is called conjugated, or direct, bilirubin. Healthy people have very little of it in their blood. The test measures it with a chemical reaction that also picks up a little albumin-bound bilirubin.
Why it matters
Because there is normally almost no direct bilirubin in the blood, a raised level is more often linked to the liver or the bile ducts than to red blood cell breakdown. Your clinician compares it with total bilirubin and with other liver tests. If most of a raised bilirubin is the direct kind, the cause is more likely in the liver or bile flow. If most of it is the indirect kind, red cell breakdown or Gilbert syndrome becomes more likely.
If it’s high
A level above your lab's range means processed bilirubin is not draining out through the bile as usual. A small rise just above the range can reflect differences in how labs measure it. Larger or lasting rises are usually looked into together with ALP, GGT, ALT and AST.
Common causes
- A small rise just above your lab's range, which can reflect differences between labs
- Inflammation of the liver, such as viral hepatitis, alcohol-related liver disease or liver injury from medicines
- Chronic liver disease, including cirrhosis
- A blocked bile duct, for example by a gallstone
- Conditions that scar or inflame the bile ducts, such as primary biliary cholangitis or primary sclerosing cholangitis
- Cholestasis of pregnancy
- Rare inherited conditions of bilirubin handling, such as Dubin-Johnson syndrome
What can help
- Ask which other liver tests, a repeat test or an ultrasound would help explain the result
- Review your medicines and supplements with your clinician
- If alcohol is a concern for your liver, talk with your clinician about it
Usual ranges
What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.
The usual range depends on age. Choose an age to see the one that applies.
- 18+0–0.4 mg/dL
Sources: Labcorp, Mayo Clinic Laboratories, MedlinePlus, National Library of Medicine
Children and teens 1 ranges
- 1–170–0.4 mg/dL
Sources: Labcorp, Mayo Clinic Laboratories
See Direct bilirubin by age and sex, with the U.S. survey numbers where they exist.
What can affect your result
- Light: bilirubin breaks down in light, so labs shield the sample
- Age: newborns have their own ranges, and Labcorp lists 0.00–0.60 mg/dL for the first 31 days
- Medicines and liver injury
- Lab method: the usual method also picks up some albumin-bound (delta) bilirubin
- Lab differences: Labcorp's adult limit is 0.4 mg/dL, while Mayo's is 0.3 mg/dL
- Bilirubin breaks down in light, so labs protect the sample from light during collection, shipping and storage (ARUP, Mayo).
- ARUP rejects hemolyzed samples and asks that serum or plasma be separated from the cells within 2 hours.
- The usual lab method also reads some albumin-bound (delta) bilirubin as 'direct', so the result is not strictly the conjugated fraction.
- A number of medicines can affect the liver or bile flow and change the result.
After a bile flow or liver problem is resolved, bilirubin falls in two steps: a quick drop, then a slower one over weeks, because part of it is bound to albumin (Giannini 2005).
When to talk to a clinician
Contact your clinician soon if your skin or eyes look yellow, your urine is dark, your stools are pale, or you have itching, belly pain or fever, especially with a raised result. In babies, the British Society of Gastroenterology guideline says a conjugated bilirubin above 25 µmol/L (about 1.5 mg/dL) needs urgent assessment by a pediatrician. Call 911 or your local emergency number for confusion, severe belly pain or fainting.
Questions you could ask
- Should we repeat this test, and when?
- Is most of my raised bilirubin the direct type, and what does that suggest?
- Which other tests, such as ALP, GGT, ALT, AST or an ultrasound, would help?
- Could a medicine or supplement be involved?
Questions people ask
What is the difference between direct and total bilirubin?
Total bilirubin is all the bilirubin in your blood. Direct bilirubin is the part your liver has already processed. A raised direct part points more toward the liver or bile ducts. A raised indirect part, which is total minus direct, points more toward red blood cell breakdown or Gilbert syndrome.
Is direct bilirubin the same as conjugated bilirubin?
They are used as the same thing on most reports. The usual lab method also picks up a little albumin-bound bilirubin, so 'direct' is not strictly the conjugated fraction alone.
Show the science and sources
Units
- 1 mg/dL = 1 mg/dL
- 1 mg/dL = 17.1 µmol/L
Open the Direct bilirubin unit converter
Is a change real?
Direct bilirubin naturally varies about 20.9% from test to test in the same healthy person. Between two results from the same lab, a rise of 82% or more, or a fall of 45% or more, is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: The European Biological Variation Study (EuBIVAS): a summary report.
For clinicians and researchers
Direct bilirubin is the fraction that reacts with diazo reagent without an accelerator. It is mostly bilirubin mono- and diglucuronide, plus some delta bilirubin (conjugated bilirubin covalently bound to albumin, with albumin's long half-life), so it is not strictly the conjugated fraction by the usual methods. Mayo lists a photometric method and ARUP quantitative spectrophotometry. In healthy people conjugated bilirubin is nearly absent from serum, and it rises when the liver has lost at least about half of its excretory capacity, so a raised value usually signals liver or biliary disease (Giannini 2005). After the cause resolves, bilirubin falls in two phases, the second tracking delta bilirubin's albumin-linked half-life (Giannini 2005). The BSG 2018 guideline notes that conjugated hyperbilirubinemia is typically due to parenchymal liver disease or biliary obstruction, and that in neonates and infants a conjugated bilirubin above 25 µmol/L needs urgent pediatric assessment of possible liver disease. Indirect (unconjugated) bilirubin is calculated as total minus direct and is carried as its own marker. Reference intervals differ slightly between labs.
LOINC 1968-7 (primary), 14629-0, 35191-6. Specimen: serum-or-plasma.
Sources
- Bilirubin, Direct (test 001222), sample report, Labcorp
- Pediatric Testing Reference Ranges, Labcorp
- Liver Profile, Serum (test ID LIVPR), Mayo Clinic Laboratories
- Bilirubin, Direct, Serum or Plasma (test 0020033), ARUP Laboratories
- Bilirubin blood test, MedlinePlus, National Library of Medicine (2025)
- Guidelines on the management of abnormal liver blood tests, Gut (British Society of Gastroenterology) (2018)
- Liver enzyme alteration: a guide for clinicians, Canadian Medical Association Journal (2005)
- Bilirubin (PubChem CID 5280352), PubChem, National Library of Medicine
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.