High bilirubin: what it means, the three causes, and when it matters

An elevated total bilirubin is a sum, and the useful part of the result is how that sum splits. Bilirubin is the yellow pigment left over when old red blood cells are broken down. The liver attaches a sugar-like molecule to it (conjugation) so it can leave in bile, and a lab reports two forms: indirect bilirubin (unconjugated, before the liver has processed it) and direct bilirubin (conjugated, after). For how the test works, see the main total bilirubin page.

A mostly indirect rise with normal liver enzymes is usually Gilbert's syndrome, which is generally harmless. A raised direct fraction means the liver or bile ducts are holding bilirubin back, and that needs a doctor ¹².

Which kind of high is yours: direct vs indirect bilirubin

Many reports print total and direct bilirubin and leave indirect bilirubin for you to work out. Indirect bilirubin equals total bilirubin minus direct bilirubin. Doctors start with one rule. If direct bilirubin is less than about 20% of the total, a high indirect bilirubin is the main story and the pattern is unconjugated, and a larger direct share points to the liver or bile ducts ¹³.

Elevated total serum bilirubin levels should be fractionated to direct and indirect bilirubin fractions and an elevated serum conjugated bilirubin implies hepatocellular disease or biliary obstruction in most settings.Kwo, Cohen and Lim, ACG Clinical Guideline: Evaluation of Abnormal Liver Chemistries, 2017 ¹

The three patterns and what goes with each

Doctors sort a high bilirubin by where the hold-up sits: before the liver, inside the liver, or after it in the bile ducts. Each pattern has its own companion markers on the same blood draw ¹².

High bilirubin with normal liver tests: Gilbert's syndrome

Gilbert's syndrome is the most common reason for a mildly high bilirubin in an adult who feels well. It is an inherited difference in the gene for the liver enzyme that processes bilirubin (UGT1A1), which leaves that enzyme working at about a third of its usual speed. Gilbert's syndrome affects about 5 to 10% of people, raises only indirect bilirubin, usually keeps total bilirubin under about 3 mg/dL, and leaves the rest of the liver panel normal ³.

Gilbert's bilirubin goes up and down. Fasting or very low calorie intake, illness, hard exercise and stress can all push it up for a few days ². Calorie restriction roughly doubles unconjugated bilirubin in people with Gilbert's syndrome, which is why it was once used as a diagnostic test ³. A result taken the morning after a long fast or a hard race can be higher than the same person's usual number.

Gilbert's syndrome needs no treatment and does not damage the liver ³. The cancer drug irinotecan is cleared by the same UGT1A1 enzyme, and people with two copies of the common Gilbert's variant (UGT1A1*28) have a higher risk of severe low white cell counts from it ⁹, so anyone with Gilbert's who is offered irinotecan should tell the oncology team, who will decide on dosing. HIV medicines called protease inhibitors, such as atazanavir, slow the same enzyme and can raise indirect bilirubin enough to cause yellowing, especially in people with Gilbert's ².

When red cells break down too fast (hemolysis)

Hemolysis means red cells are being destroyed faster than normal, which floods the liver with unconjugated bilirubin. Hemolysis is confirmed by a cluster of markers moving together: LDH up (released from broken cells), haptoglobin down (used up mopping free hemoglobin), reticulocytes up (the bone marrow making replacements), and often hemoglobin down ⁴. Hemolysis on its own usually raises bilirubin only mildly, rarely above about 5 mg/dL ⁷; a higher number makes a doctor look for a liver problem as well.

Common adult causes include inherited red cell conditions such as hereditary spherocytosis, sickle cell disease and G6PD deficiency (where certain drugs or fava beans set off breakdown), autoimmune hemolytic anemia, a mechanical heart valve, and the breakdown of a large bruise or internal bleed ⁷. Sudden dark urine, yellowing and breathlessness after a trigger needs same-day care. Tiredness, breathlessness and a fast heartbeat point toward the anemia side of the picture; the anemia page covers it.

High direct bilirubin: liver or bile duct

High direct bilirubin means the liver has conjugated bilirubin but cannot get it out, either because liver cells are injured or because bile cannot drain. The enzymes on the same report usually show which. A cholestatic pattern (bile not flowing), with ALP high and GGT high out of proportion to ALT, points to the bile ducts. A hepatocellular pattern (liver cells damaged), with ALT and AST high out of proportion to ALP, points to hepatitis, alcohol, fatty liver disease or drug injury ¹.

The common causes of a high direct bilirubin in adults are a gallstone lodged in the common bile duct, alcohol-related and viral hepatitis, advanced fatty liver disease, and injury from medicines or supplements ². Some antibiotics, the contraceptive pill and anabolic steroids are classic medicine causes ⁷, and concentrated green tea extract is one of the best-documented supplement causes ⁸. Two rare inherited conditions, Dubin-Johnson and Rotor syndromes, raise direct bilirubin by slowing its exit from liver cells ⁷. An abdominal ultrasound is the usual first scan, because it is the least invasive way to tell a blocked duct from a liver cause ².

Direct bilirubin can stay high for weeks after a blocked duct is cleared. Some of it sticks firmly to albumin and only clears as the body replaces albumin, which takes about 2 to 3 weeks for half of it ⁵. A slow fall after a gallstone is removed is expected.

What your number means: 1.3, 1.5, 2, 3 and above

The fraction and the other markers on the report matter more than the number itself, but rough bands help when you are reading a bilirubin of 1.6 or 2. To convert, 1 mg/dL of bilirubin equals 17.1 µmol/L ¹; the lab units guide explains why reports differ.

At any level, a raised bilirubin with dark urine, pale stools or a high ALT needs prompt medical review.

Symptoms: yellow eyes, dark urine, pale stools, itch

Most people with a mildly high bilirubin have no symptoms. Higher levels yellow the whites of the eyes first, then the skin ⁷. Only conjugated bilirubin dissolves in water and can pass into urine, so dark, tea-colored urine and a positive urine bilirubin point to a liver or bile duct cause ⁷. Urine bilirubin stays negative in Gilbert's syndrome and in hemolysis. Sudden severe hemolysis is the exception to normal-looking urine: free hemoglobin can turn urine red-brown or cola-colored, and that needs same-day care. Pale or clay-colored stools mean bile is not reaching the gut, and itching, fever and belly pain can come with a blocked duct ². The urinalysis guide explains the urine side.

When high bilirubin is urgent

ALT above 3 times the upper limit plus total bilirubin above 2 times the upper limit, without a blocked duct to explain it, is a warning sign doctors call Hy's law. It marks the more serious kind of medicine-related liver injury: about 10% or more of these cases end in death or a liver transplant ⁶. If a result like that follows a new prescription, over-the-counter medicine or supplement, call the prescriber or a doctor the same day. They will usually advise stopping a new supplement, and a prescribed medicine should not be stopped without their advice.

What to do next with a high result

1. 1Check the splitFind direct bilirubin on the report and work out its share of the total. Under about 20% is an unconjugated pattern; above that points to the liver or bile ducts ¹³.
2. 2Read the rest of the reportLook at ALT, AST, ALP and GGT and the blood count on the same draw. Normal enzymes and a normal hemoglobin with a mostly indirect rise fit Gilbert's syndrome. The liver enzymes guide covers the enzymes.
3. 3Think back over the days before the testFasting, a missed meal, a recent illness, hard training, and any new medicine or supplement can all raise bilirubin.
4. 4Repeat the test after normal eating and restA repeat in a few weeks, after normal meals and no hard exercise the day before, shows whether the rise is a one-off. Use the same lab if you can, because labs use slightly different methods. The guide to preparing for a blood test has the details, and why a trend beats a single reading explains why one value is not enough.
5. 5Let a doctor add what fits the patternAn indirect rise may lead to LDH, haptoglobin and reticulocytes; a direct rise to an abdominal ultrasound and hepatitis tests ¹². Any of the red flags above, such as dark urine with pale stools or new yellow eyes, means booking that review the same day.

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Lowering bilirubin means treating whatever is raising it: removing a duct stone, stopping an offending medicine under medical advice, managing hemolysis or liver disease. Gilbert's syndrome needs nothing beyond regular meals, since fasting is the main thing that lifts it ³. No supplement has good evidence for lowering bilirubin. Milk thistle is the one most often suggested, and its trials look at liver enzymes in liver disease rather than at bilirubin.

The supplement people ask about

Weak evidenceMilk thistleStudied for liver enzymes in fatty liver and hepatitis with mixed results; no good evidence that it lowers bilirubin or helps Gilbert's syndrome.In our shop

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