Diagnosing Gilbert's syndrome
NHS Choices Medical Reference
Gilbert's syndrome is often diagnosed in the late teens or early twenties. It is fairly easy to diagnose, so there is usually no need to do a genetic test for it.
Your GP will take a blood sample and do a full blood count. They will also test how well your liver is working and check your bilirubin levels. If there are high levels of water-insoluble bilirubin but the other tests are normal, this is usually because of Gilbert's syndrome.
If you have jaundice, your doctor will run some tests to rule out other possible causes that are more serious than Gilbert's syndrome, such as liver disease.