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Indirect Bilirubin

LFT Biomarker

Sample Needed

Collection Type: Blood

Body System

Related System: LFT

Overview

Indirect bilirubin (unconjugated bilirubin) is the lipid-soluble form of bilirubin produced when hemoglobin from aging red blood cells is broken down. It circulates bound to albumin and is taken up by the liver for conjugation (making it water-soluble) and excretion. The indirect bilirubin test measures the unconjugated fraction (often calculated as total minus direct bilirubin) and helps identify causes of jaundice such as hemolysis, impaired hepatic uptake/conjugation (e.g., Gilbert syndrome), and neonatal physiologic jaundice. Symptoms that prompt testing include yellowing of skin/eyes, fatigue or dark urine (note: dark urine usually reflects conjugated bilirubin). Levels vary by age—newborns commonly have higher indirect bilirubin—and are only modestly affected by sex.

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Test Preparation

No special preparation is required

Why Do I Need This Test

Profile: included in liver function tests (LFT) / bilirubin panel.
Symptoms prompting testing: jaundice, pallor, unexplained fatigue, dark urine or light stools (to evaluate type of jaundice).
Conditions diagnosed/monitored: hemolytic anemias, Gilbert syndrome, Crigler–Najjar, neonatal jaundice, impaired hepatic uptake.
Reasons for abnormal levels: increased production (hemolysis), decreased hepatic uptake or conjugation, genetic disorders, certain drugs, fasting.
Biological meaning: elevated indirect bilirubin indicates increased production or reduced hepatic processing; lifestyle factors like fasting, dehydration, or certain medications can raise levels.
Family history: hereditary unconjugated hyperbilirubinemias or hemolytic disorders warrant testing.

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Understanding Test Results

Within normal (0.2–0.8 mg/dL): expected in healthy adults.
Mild elevation (~0.8–2.0 mg/dL): commonly seen with Gilbert syndrome, mild hemolysis, or transient factors (fasting, illness, certain medications).
Often asymptomatic apart from mild jaundice.
Moderate elevation (≈2.0–5.0 mg/dL): suggests significant hemolysis, more pronounced impairment of hepatic uptake/conjugation, or worsening inherited disorders; warrants evaluation for hemolytic markers and liver function.
Marked elevation (>5.0 mg/dL): uncommon in adults; indicates severe hemolysis or major conjugation failure (e.g., Crigler–Najjar) and requires urgent evaluation.
In neonates, high unconjugated bilirubin carries risk of bilirubin encephalopathy (kernicterus) and needs prompt treatment.
Low values (<0.2 mg/dL): rarely clinically meaningful; may reflect lab variation.
Note: unconjugated bilirubin is not water-soluble and will not appear in urine—presence of bilirubin in urine points to elevated conjugated bilirubin.

Normal Range

0.2-0.8 mg/dL OR 3.4-13.7 μmol/L

FAQs

Q: What does it mean if indirect bilirubin is high?

A: High indirect (unconjugated) bilirubin means there’s excess unconjugated bilirubin in the blood, usually from increased red blood cell breakdown (hemolysis) or reduced hepatic uptake/conjugation (genetic conditions like Gilbert’s, neonatal immaturity, or drug effects). It commonly causes jaundice but typically not dark urine. Further evaluation (blood counts, liver tests, and specific enzyme/genetic testing) determines the cause and treatment.

Q: How can I reduce indirect bilirubin?

A: To reduce indirect (unconjugated) bilirubin, treat the underlying cause: correct hemolysis (fluids, transfusion or immunosuppression if autoimmune), manage inherited disorders and hypothyroidism, and avoid triggers (fasting, dehydration, alcohol, certain drugs). Maintain good hydration and nutrition, address infections, and follow physician-directed therapies (phototherapy or exchange transfusion in newborns). Seek prompt medical evaluation and periodic testing.

Q: What is the indirect bilirubin level for jaundice?

A: Jaundice usually appears when total bilirubin rises above about 2–3 mg/dL (34–51 µmol/L). Indirect (unconjugated) bilirubin levels contributing to jaundice are typically above ~1.5–2 mg/dL (25–34 µmol/L). Normal indirect bilirubin is roughly 0.2–1.2 mg/dL (3–20 µmol/L). Consult a clinician for interpretation.

Q: Is 1.5 indirect bilirubin high?

A: An indirect (unconjugated) bilirubin of 1.5 mg/dL is mildly elevated above typical laboratory reference ranges. Causes include Gilbert syndrome, increased red‑cell breakdown (hemolysis), or reduced liver uptake. Your clinician may repeat the test, check direct bilirubin, liver enzymes, CBC, reticulocyte count and hemolysis markers, and consider further evaluation. Discuss results with your healthcare provider for next steps.

Q: Can dehydration cause high indirect bilirubin?

A: Dehydration does not typically cause a marked increase in indirect (unconjugated) bilirubin. Severe dehydration can reduce liver perfusion and cause mild transient rises, and hemoconcentration may slightly elevate measured bilirubin. Persistent or significant unconjugated hyperbilirubinemia suggests hemolysis, Gilbert’s syndrome, or uptake/conjugation problems rehydrate, repeat tests, and seek medical evaluation if levels remain high.

Q: What foods cause high bilirubin?

A: Few foods directly raise bilirubin; factors that worsen liver function or trigger hemolysis can. Avoid alcohol and very fatty, highly processed or high‑fructose diets that promote fatty liver; steer clear of some herbal supplements and toxins. People with G6PD deficiency should avoid fava beans and other oxidative foods/medications that cause hemolysis. See a clinician for specific advice and testing.