Most patients with Gilbert's syndrome have no symptoms. The disorder is frequently diagnosed by coincidence when a lab test done for another reason such as a life insurance examination, shows an abnormally high amount of unconjugated bilirubin.
The level of bilirubin can fluctuate in people with Gilbert's syndrome. They may be highest after an infection (such as flu), following periods of fasting, and after menstrual periods in some women.
Because males tend to produce higher levels of bilirubin, the disorder is more likely to be detected in men. Similarly, it is rarely diagnosed before puberty because production of bilirubin increases at this point.