Conditions · Metabolism: heme, bilirubin and iron
Gilbert syndrome !
A benign inherited condition in which the liver conjugates less bilirubin; it causes mild jaundice with fasting, stress or infection.
Updated 2026-11-01
Structures involved
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In biochemistry
- Liver function tests: reading the pattern
- Uronic acid pathway
- UGT1A1 (bilirubin UDP-glucuronosyltransferase)
- Bilirubin
- Glucuronidation
In the clinical exam
In physiology
What it is
Mild, fluctuating unconjugated hyperbilirubinemia from reduced expression of liver UGT1A1, without hemolysis or liver disease.
Who gets it
Very common: it affects about 3–7 % of the population; it is found in adolescence or adulthood, often on routine tests. More evident in men.
Causes
- UGT1A1*28 variant (extra TA repeats in the promoter), usually on both alleles
- Other UGT1A1 variants, more common in Asia
Risk factors
- Fasting or a very low-calorie diet
- Infections, strenuous exercise, menstruation, lack of sleep
Pathophysiology
UGT1A1 works at about 30 % of normal. Indirect bilirubin builds up slightly, especially when fasting raises the load or slows conjugation. Liver tests are normal and there is no liver damage.
Symptoms and signs
- Mild, intermittent yellowing of the sclerae
- Most have no other symptoms
- Sometimes fatigue or vague abdominal discomfort
Diagnosis
- Clinical
- Mild recurrent jaundice brought on by fasting or illness, with a normal physical examination.
- Tests
- Mildly raised indirect bilirubin (usually below 3–4 mg/dL), normal direct bilirubin, normal transaminases and alkaline phosphatase; blood count and reticulocytes to rule out hemolysis; UGT1A1 genotype if in doubt.
- Imaging
- Not needed; liver ultrasound only if other tests are abnormal.
Treatment
- Conservative
- No treatment is needed; explaining that it is benign avoids unnecessary investigations
- Follow-up
- Caution with drugs cleared by UGT1A1, such as irinotecan
Complications
- Greater irinotecan toxicity
- Possibly more gallstones when hemolysis coexists
Prognosis
Excellent; life expectancy is normal.
Test yourself
Think of the answer, then tap the question to see it.
Which bilirubin fraction rises in Gilbert syndrome?
Unconjugated (indirect) bilirubin.
What triggers jaundice in Gilbert syndrome?
Fasting, infection, stress, strenuous exercise and menstruation.
Which gene and variant most often cause Gilbert syndrome?
UGT1A1, promoter variant *28 (extra TA repeats).
Related conditions
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Gilbert syndrome: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); UGT1A1 gene: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); Bilirubin blood test: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026).
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Representative model, for educational purposes only.
