At a Glance
This test measures direct bilirubin in a serum or plasma sample, reported in mg/dL. The interval stored here is 0 to 0.4 mg/dL, and that is the interval your result on this page is flagged against.
It is not the only published one. Mayo Clinic Laboratories publishes 0.0 to 0.3 mg/dL for ages twelve months and over, and states that reference values have not been established below twelve months. So a result of 0.35 sits inside the interval on this page and above Mayo's — a tenth of a milligram per deciliter between two laboratories' reference limits, which is the ordinary kind of difference between laboratories rather than a puzzle.
Direct bilirubin is also not reported alone. Labcorp's test 001214 lists what arrives on the report as "Bilirubin, conjugated (direct); bilirubin, indirect; bilirubin, total", and Mayo states plainly what follows: "Direct bilirubin levels must be assessed in conjunction with total and indirect levels and the clinical setting."
What follows keeps three kinds of number apart: a laboratory's reference limit, a condition's definition, and an infant's result.
The reference limit your result was compared against
This is the number that decides whether your result shows as high, and it is a laboratory's answer to one narrow question: what range does this laboratory, on this assay, treat as unremarkable.
0 to 0.4 mg/dL is the interval stored on this page. 0.0 to 0.3 mg/dL is Mayo's, for ages twelve months and over. Both are reference limits for the same test, so they are directly comparable, and they differ by a tenth. That is why a result of 0.35 or 0.4 can be flagged on one report and not another, and it is the entire answer to "is 0.4 high" at the level of the number alone.
What a reference limit does not do is tell you what a result outside it means for you. For that, Mayo names three inputs — your total, your indirect and the clinical setting — and only the first two are printed on your report.
A different question: what clinicians call conjugated hyperbilirubinemia
The figures in the next paragraph are not reference limits and they are not a tighter version of one. They belong to a different question: when does a raised direct bilirubin amount to a named condition. Mixing the two kinds together is the misreading this page is written to prevent.
StatPearls defines pathologic elevation of conjugated or direct bilirubin — "concentration higher than 2 mg/dL or more than 20% of total bilirubin" — as conjugated hyperbilirubinemia, and calls it "a biochemical marker of cholestasis and hepatocellular dysfunction". The chapter attributes that pair to a 2007 review.
Two things to notice. 2 mg/dL is a higher number than 0.4, not a stricter one — applied to the same results it would flag fewer of them, which is a sign it is answering a different question rather than competing with the reference limit. And the 20% share is the limb that can be met at small concentrations, because the direct fraction is normally a minority of the total. Your direct result divided by your total is arithmetic you can do from your own report, and a share above a fifth is a thing worth raising with whoever ordered the test.
It is not a verdict, and the same chapter says why. Under Evaluation, StatPearls records: "No consensus of direct bilirubin levels defining conjugated hyperbilirubinemia was encountered." That statement is about this definition — the levels at which the condition is said to begin — and not about the reference limits above, which are ordinary laboratory numbers and are not in doubt.
What "direct" actually measures
The name comes from chemistry, not from being straightforward. StatPearls describes direct bilirubin as the fraction that "reacts readily when reagents are added to the blood specimen", while indirect bilirubin reacts "solely following the addition of accelerants like caffeine or methanol". And "total bilirubin tallies direct and indirect bilirubin levels".
What that fraction contains is wider than the word "conjugated" suggests, and LOINC says so: "Prior to the discovery of albumin-bound bilirubin, the term 'direct' bilirubin was used as a synonym for glucuronidated bilirubin, but direct bilirubin is actually glucuronidated plus delta bilirubin (bilirubin covalently bound to albumin)." That is why LOINC names the component of this test "Bilirubin.glucuronidated+Bilirubin.albumin bound".
Delta bilirubin got its name from an arithmetic surprise. LOINC describes it as bilirubin bound to albumin, "also known as delta bilirubin because it was originally identified based on the unexpected difference between the total bilirubin level and the level of glucuronidated plus non-glucuronidated bilirubin in some patient samples." The two known fractions did not add up to the total, and the shortfall was a third form. StatPearls adds why it lingers: albumin binding stops being readily reversible, and albumin's half-life is around 21 days.
Two qualifications belong here. LOINC's term description opens "Except when measured by differential light absorption" — a method under which the albumin-bound fraction is not included. And it records that the method "can be WET CHEMISTRY or DRY SLIDE = (TBIL-Bu)" — the last term being total bilirubin minus the unconjugated fraction, so where a laboratory works that way your direct value is a difference between two larger measurements rather than a reading of its own.
How to read your result
0.3 mg/dL or below. Inside the interval stored here and inside Mayo's. Neither reference limit marks it.
Above 0.3, up to and including 0.4 mg/dL. Inside the interval stored here, above Mayo's. Not flagged on this page; would be on that one. This band is two laboratories' reference limits differing by a tenth, not a finding about you.
Above 0.4 mg/dL. Flagged here, against the interval stored on this page. What it is worth depends on what this page cannot see: your total and indirect results, whether the value has moved on repeat testing, your other liver tests, and the clinical setting.
Your direct result as a share of your total. Worth working out, since both numbers are on the report. More than 20% of the total is one of the two criteria StatPearls gives for conjugated hyperbilirubinemia — a thing to raise, not a result in itself.
Above 2 mg/dL. The concentration limb of that definition, stated as higher than 2 mg/dL. Several times above the results this page is usually read for.
Any result in an infant. Not covered by anything above. See below.
If you remember only one thing
Your direct bilirubin and your total bilirubin are one reading, not two. Which reference limit flagged yours matters, because laboratories differ by a tenth — and what the flag means needs both numbers plus a clinical setting no report carries.
Two people, same result
Two people are each told their direct bilirubin is 0.5 mg/dL.
The first has a total bilirubin of 2.6, so the direct fraction is about 19% and the indirect fraction carries the other 81%. The larger part of this person's raised total is the indirect form.
The second has a total bilirubin of 1.0. The direct fraction is 50%, and the two forms are split evenly.
Same direct number, two different readings. All that shows is that a direct result reported alone is incomplete — not that either person is well or unwell.
What this result cannot tell you
It cannot tell you what a result just outside its reference limit means for you. A reference limit sorts results as usual or unusual for that laboratory's population; it does not interpret one. Mayo names the three inputs that do, and the clinical setting is not on any report.
It cannot tell you why a raised direct fraction is raised. StatPearls describes conjugated hyperbilirubinemia as "usually secondary to hepatocellular disease or cholestasis (intrahepatic and extra-hepatic)" — a category rather than an answer.
It cannot separate the causes on the other side of the total. Labcorp frames what the three bilirubin numbers tell apart: "bilirubin overproduction (hemolysis), decreased uptake (Gilbert disease), decreased conjugation (hepatocellular disease, familial, drug-induced, pregnancy…)". Those live largely in the indirect fraction.
It cannot be read across laboratories as one series. The reference limits differ, and LOINC's term description names more than one way the value is obtained.
It cannot be used for an infant. Mayo states reference values are not established below twelve months. Infant jaundice is assessed by pediatric criteria that this page does not reproduce, and an infant's bilirubin result belongs with the clinician looking after the baby, promptly.
Common interpretation mistakes
Reading the direct value without the total. The two are reported together and Mayo says explicitly that they must be read together.
Treating 0.4 as a boundary in nature. It is the reference limit stored on this page; Mayo publishes 0.3 for the same test, and the method can differ too, so a result is read against its own laboratory's interval.
Reading the 2 mg/dL figure as a stricter version of the reference limit. It is a higher number answering a different question — when a raised direct bilirubin amounts to a named condition — and it would flag fewer results, not more.
Treating the 20% share as a verdict. It is one of two criteria for a pathologic elevation, and the chapter that gives it reports no consensus on the levels defining that condition.
Reading "direct" as "conjugated". LOINC states that direct bilirubin is glucuronidated plus delta bilirubin, and that the synonym predates the discovery of the albumin-bound form.
Assuming a low or undetectable direct bilirubin is a deficiency. It is the expected finding.
Applying any of this to a newborn. Infant jaundice has its own criteria and its own urgency.
Questions your doctor may ask
What your total and indirect bilirubin were on the same sample — Mayo names both, and the clinical setting, as what this result must be read with. Whether your liver enzymes were measured alongside. Whether the value has been measured before, and what it was. Whether you have noticed any yellowing of the skin or eyes, since Mayo gives evaluation of jaundice as what the test is for. What medicines and supplements you take, which is in the differential Labcorp sets out. And whether anyone has mentioned Gilbert syndrome to you before, which sits in that differential on the indirect side.
Read together with
Bilirubin Total, Bilirubin Indirect, Alanine Aminotransferase, Aspartate Aminotransferase, Alkaline Phosphatase and Gamma-Glutamyl Transferase. The first two are what make this number readable at all — Mayo names total and indirect explicitly. The liver enzymes are what a clinician reads alongside it, and StatPearls names the two categories they are being used to tell apart: cholestasis and hepatocellular disease.
Clinical pearls
Mayo cautions that grossly hemolyzed specimens "should be rejected because hemoglobin inhibits the diazo reaction which may cause falsely low results". Note what that is and is not: a conditional caution about gross hemolysis on Mayo's own assay, not a rule that every imperfect sample reads low.
The same source instructs that specimens "should be protected from light and analyzed as soon as possible". Bilirubin is light-sensitive, and a delayed or exposed sample is a sample with a reason to be wrong.
Delta bilirubin explains a result that stays up after the problem is settled: because it is bound to albumin, and albumin's half-life is around 21 days, it clears on albumin's schedule rather than bilirubin's.
Mayo's stated use for this test is "evaluation of jaundice and liver functions" — a test for a question already being asked, worth knowing if it arrived inside a panel rather than because someone was looking for something.
Clinical Takeaway
At 0.3 or below, both reference limits on this page agree there is nothing to mark. Above 0.3 and up to 0.4, the two laboratories differ by a tenth. Above 0.4 this page flags it, and what follows is a reading rather than a calculation: the total and indirect beside it, the share they imply, whether the number has moved, the other liver tests, and the clinical setting Mayo names as the third input. The 2 mg/dL and 20% figures answer a different question — when a raised result amounts to conjugated hyperbilirubinemia — and the chapter giving them reports no consensus on that condition's defining levels. An infant's result is outside all of it.
In one sentence
A direct bilirubin of a few tenths is read against your own laboratory's reference limit, which can differ from another's by a tenth, then interpreted with the total and indirect beside it and a clinical setting no report carries.
Bottom line
Look at the number next to it, and at which reference limit flagged yours. The share of your total is worth working out and worth raising. Neither is a verdict.
Bilirubin Direct
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Frequently Asked Questions
Is a direct bilirubin of 0.4 high?
What does a direct bilirubin of 0.5 or 0.6 mean?
What is the normal range for direct bilirubin?
What is the difference between direct and indirect bilirubin?
Is direct bilirubin the same as conjugated bilirubin?
My direct bilirubin is high but my total is normal. What does that mean?
Can a blood draw or sample problem change my direct bilirubin?
Can direct bilirubin be too low?
Does this page's range apply to a baby?
All our content is backed by peer-reviewed studies, academic research, and trusted medical sources. We’re committed to accuracy and transparency — see our editorial policy for details.
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Conjugated Hyperbilirubinemia
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LOINC 1968-7 — Bilirubin.direct [Mass/volume] in Serum or Plasma
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Bilirubin, Direct, Serum — test BILID
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Bilirubin, Total and Direct — test 001214