July 14, 2020
Fasting Test for the Diagnosis of Gilbert's Syndrome Minimize

Fasting test for the diagnosis of Gilbert's syndrome


Gilbert's syndrome is a relatively common cause of an unconjugated hyperbilirubinaemia often only uncovered when a minor elevation in plasma bilirubin does not fall after a mild illness. It is probably the result of a heterogeneous group of disorders some of which have a defect in the uptake of organic anion by the liver. Total bilirubin concentrations in this condition are usually in the range 21-51 micromol/L and rarely rise above 86 micromol/L. The total bilirubin fluctuates with intercurrent illness, physical exertion and stress.

The diagnosis of Gilbert's syndrome is predominantly by the exclusion of other conditions. This fasting test may aid the diagnosis but does not give a definitive separation from hepatitis.



Side effects



no specific patient preparation required


2 biscuits

2 Lithium heparin tubes


Plasma bilirubin concentrations rise after fasting and other forms of metabolic stress eg surgery, fever or infection in all individuals but the change is more marked in subjects with Gilbert's. This mechanism for this effect is unknown but is probably related to hepatic clearance, rather than increased production, of bilirubin. This has been proposed to be due to competition by free fatty acids for the intracellular bilirubin binding protein.


Day 1: take blood for total and unconjugated plasma bilirubin estimations: begin calorie restriction to 300 kcal per day (approximately 2 biscuits)

Day 2: take blood for total and unconjugated plasma bilirubin estimations

End of investigation


Total bilirubin concentrations rise in normal individuals by approximately 60% after 48h fasting whereas in subjects with Gilbert’s syndrome the total bilirubin concentration rises by approximately 90% after 24h. The unconjugated bilirubin concentration rises by more than 110% after 24h.


  • Olsson R, Lindstedt G. Evaluation of tests for Gilbert's syndrome. Acta Med Scand 1980;207:425-428.
  • Owens D, Sherlock S. Diagnosis of Gilbert's syndrome: role of reduced caloric intake test. Br Med J 1973;3:559.
  • Thomsen HF, Hardt F, Juhl E. Diagnosis of Gilbert's syndrome. Reliability of the caloric restriction and phenobarbital stimulation tests. Scand J Gastroenterol 1981;16:699-703.

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