High Bilirubin Levels Explained
What elevated bilirubin means, direct vs indirect, Gilbert syndrome, and when jaundice is serious — written for Australian patients by health data analysts.
What Is Bilirubin?
Bilirubin is a yellow pigment produced when your body breaks down old red blood cells. This is a normal, continuous process — your body recycles about 1% of its red blood cells every day. The haemoglobin released is converted to unconjugated (indirect) bilirubin, which travels to the liver bound to albumin.
In the liver, bilirubin is conjugated (made water-soluble) by the enzyme UGT1A1, then excreted into bile. Bile flows into the intestine, where bacteria convert bilirubin into the pigments that give stool its brown colour and urine its yellow colour.
Bilirubin Ranges and Thresholds
Australian labs report bilirubin in µmol/L. Understanding the difference between total, direct, and indirect bilirubin is essential.
Total bilirubin (adults)
The combined measurement of conjugated (direct) and unconjugated (indirect) bilirubin.
Direct (conjugated) bilirubin
Water-soluble bilirubin processed by the liver. Elevated direct bilirubin points to liver or bile duct problems.
Indirect (unconjugated) bilirubin
Fat-soluble bilirubin not yet processed. Elevation suggests haemolysis or Gilbert syndrome.
Gilbert syndrome range
Typically fluctuating, predominantly unconjugated. Rises with fasting, stress, illness, or exercise. Completely benign.
Clinical jaundice threshold
Visible yellowing of skin and whites of eyes (scleral icterus) usually becomes apparent above this level.
Newborn bilirubin (term, day 3–5)
Neonatal jaundice is common and usually physiological. Treatment thresholds depend on age in hours and risk factors.
Direct vs Indirect — The Diagnostic Key
The pattern of bilirubin elevation immediately narrows the differential diagnosis. This is why your GP requests a "split bilirubin" rather than just total bilirubin.
Indirect (unconjugated)
Mechanism: Bilirubin produced faster than the liver can process it
Common causes: Gilbert syndrome, haemolytic anaemia, large haematoma reabsorption, ineffective erythropoiesis
Direct (conjugated)
Mechanism: Liver processes bilirubin but cannot excrete it into bile
Common causes: Gallstones, pancreatic cancer, cholangiocarcinoma, primary biliary cholangitis, drug-induced cholestasis
Mixed (both elevated)
Mechanism: Liver cell damage impairs both conjugation and excretion
Common causes: Viral hepatitis, alcoholic hepatitis, paracetamol toxicity, advanced cirrhosis, autoimmune hepatitis
Common Causes of High Bilirubin
Gilbert syndrome is the most common cause of isolated, mild elevation. Liver disease and haemolysis cause more significant elevations.
Gilbert syndrome
The most common cause of isolated mildly elevated bilirubin, affecting 5–10% of the population. A harmless genetic variant reduces the liver enzyme (UGT1A1) that conjugates bilirubin. Levels fluctuate with fasting, stress, and illness. No treatment needed — it is NOT a disease.
Haemolytic anaemia
When red blood cells are destroyed faster than normal, more haemoglobin is converted to bilirubin than the liver can process. Causes include autoimmune haemolysis, hereditary spherocytosis, G6PD deficiency, and sickle cell disease.
Hepatitis (viral)
Hepatitis A, B, C, and E can cause liver inflammation that impairs bilirubin processing. Both direct and indirect bilirubin rise. Usually accompanied by elevated ALT, AST, and symptoms. Hepatitis B and C are common in Australia.
Alcohol-related liver disease
Chronic alcohol use damages liver cells, reducing their ability to conjugate and excrete bilirubin. Jaundice in the context of heavy drinking is a serious warning sign of advanced liver disease.
Gallstones (choledocholithiasis)
A stone blocking the common bile duct prevents conjugated bilirubin from reaching the intestine. Direct bilirubin rises sharply, urine turns dark, and stools become pale. Requires urgent intervention.
Medications
Many drugs can raise bilirubin. Atazanavir (HIV medication) inhibits UGT1A1 like Gilbert syndrome. Rifampicin, flucloxacillin, and some herbal supplements can cause cholestatic liver injury. Paracetamol overdose causes acute hepatocellular damage.
Fatty liver disease (NAFLD/MASLD)
The most common chronic liver condition in Australia, affecting about 25% of adults. In advanced stages, inflammation and fibrosis impair liver function and bilirubin may rise.
Newborn jaundice
Extremely common in the first week of life. Neonates have high red cell turnover, immature liver enzymes, and increased enterohepatic circulation. Physiological jaundice peaks at day 3–5 and resolves by 2 weeks.
What Your GP Will Do Next
The investigation pathway depends on whether bilirubin is direct, indirect, or mixed.
1. Check the split: direct vs indirect
The most important first step is determining whether the elevated bilirubin is predominantly direct or indirect. This immediately narrows the differential diagnosis.
2. Review liver function tests
ALT, AST, ALP, GGT, and albumin provide crucial context. Normal liver enzymes with isolated indirect hyperbilirubinaemia strongly suggests Gilbert syndrome.
3. Full blood count and reticulocytes
If indirect bilirubin is elevated, your GP will check for haemolysis: low haemoglobin, high reticulocytes, low haptoglobin, and high LDH.
4. Consider Gilbert syndrome
If you are young, bilirubin is mildly elevated (20–50), predominantly unconjugated, liver enzymes are normal, and haemolysis has been excluded — the diagnosis is almost certainly Gilbert syndrome. No further investigation is needed.
5. Liver ultrasound
If direct bilirubin is elevated or liver enzymes are abnormal, an ultrasound checks for gallstones, bile duct dilation, liver size, fatty liver, and masses. Medicare-covered and non-invasive.
6. Specialist referral
Gastroenterologist or hepatologist referral if: persistently elevated bilirubin with abnormal liver function, suspected gallstone obstruction, hepatitis requiring treatment, or unexplained jaundice.
Frequently Asked Questions
I was told I have Gilbert syndrome. Should I be worried?
No. Gilbert syndrome is NOT a disease — it is a common, harmless genetic variant affecting 5–10% of the population. Your liver works perfectly well. No treatment is needed, and it has no effect on your life expectancy. The only practical implication is that some medications are metabolised by the same enzyme, so tell your doctors about it.
What does it mean if my eyes are yellow?
Yellowing of the whites of the eyes (scleral icterus) is usually the first visible sign of jaundice, typically appearing when bilirubin exceeds 40–50 µmol/L. If you notice new jaundice, see your GP promptly — while Gilbert syndrome is benign, jaundice can also indicate serious conditions.
Can diet or supplements lower bilirubin?
In Gilbert syndrome, there is no need to lower bilirubin (it is not harmful). For liver-related elevation, treating the underlying cause is what lowers bilirubin — not supplements. Be cautious with herbal liver "detox" products, which can paradoxically cause drug-induced liver injury.
What is the difference between jaundice in adults and newborns?
Newborn jaundice is extremely common (60% of term babies) and usually physiological. Adult jaundice is always pathological and requires investigation. Treatments differ too: newborns receive phototherapy, while adults need treatment of the underlying cause.
Can paracetamol cause high bilirubin?
At normal doses (up to 4g/day for adults), paracetamol rarely affects bilirubin. In overdose, paracetamol causes severe liver damage that can dramatically raise both bilirubin and liver enzymes. Always follow dosing guidelines.
My bilirubin was high but all other liver tests are normal. What does that mean?
Isolated elevated bilirubin (total 20–50 µmol/L) with completely normal ALT, AST, ALP, GGT, and albumin is the classic pattern for Gilbert syndrome. This is the most common scenario and is benign.
Related Reading
Track Your Liver Function Over Time
Upload your blood test results and SmarterBlood will chart your bilirubin, ALT, GGT, and other liver markers automatically — showing trends your GP needs to see.
This information is based on guidelines from the Royal College of Pathologists of Australasia (RCPA), Gastroenterological Society of Australia (GESA), and the Australian Liver Association. Reference ranges may vary between pathology providers. SmarterBlood provides educational information only and is not a substitute for professional medical advice.