June 16, 2025, 2:02 am | Read time: 5 minutes
Yellowish discolored eyes and diffuse fatigue—initial signs of Gilbert’s syndrome (known as Morbus Meulengracht in German)—can seem alarming at first glance but are often misunderstood. These symptoms actually indicate a metabolic disorder that, while chronic, is generally harmless. Many affected individuals remain unaware of their diagnosis for a long time or misinterpret the symptoms.
Gilbert’s Syndrome is also known as “Gilbert-Meulengracht syndrome” and is considered a widespread, genetically determined metabolic disorder. FITBOOK editor Michel Wingens explains what it is exactly, what current studies show about it, and which strategies can help in dealing with the diagnosis.
Overview
What Is Gilbert’s Syndrome?
Gilbert’s syndrome is a genetically determined metabolic variant characterized by a harmless liver dysfunction. About five to ten percent of the population is affected by it.1 The syndrome often first appears during puberty when the sex organs change. These hormonal changes can increase bilirubin levels, which can subsequently lead to jaundice in certain parts of the body. The male body also produces more bilirubin than the female body, which is why the syndrome is more noticeable in men. The syndrome predominantly occurs between the ages of 15 and 40 and can regress later in life.2
The cause is a defect in the UGT1A1 gene, which encodes an enzyme that makes bilirubin water-soluble in the liver. In people with Gilbert syndrome, this process works more slowly. The result: unconjugated (non-water-soluble) bilirubin accumulates in the blood.
Morbus Meulengracht or Gilbert Syndrome – Where Does the Name Come from?
The two terms mean the same thing—but the origins are internationally different. In German-speaking countries, the term “Morbus Meulengracht” is used, with “Morbus” being Latin for “disease.” In the DACH region (Germany, Austria, Switzerland), it is named after the Danish doctor Jens Einar Meulengracht3, who extensively studied liver diseases. It is more commonly referred to as Gilbert syndrome in international medicine and is named after the French doctor Augustin Nicolas Gilbert, who first scientifically described the condition in 1901.4
What Are the Symptoms of Morbus Meulengracht?
One of the most noticeable features of Morbus Meulengracht is a temporary yellowing of the skin and especially the whites of the eyes (sclera)—medically known as jaundice. This is caused by an elevated level of unconjugated bilirubin in the blood, which mainly occurs when the body’s metabolism is under stress. Typical stressors include:
- Fasting periods
- Physical exertion
- Fever
- Stress
- Menstruation and pregnancy
- Alcohol, smoking, and medications
For most affected individuals, the yellowing is the only symptom and is harmless, usually disappearing on its own once the body stabilizes. Often, elevated bilirubin levels are discovered incidentally during routine lab tests, without any visible symptoms.
Occasionally, affected individuals report additional nonspecific symptoms such as fatigue, concentration problems, or mild nausea. However, a direct connection with bilirubin levels has not been scientifically established.
Rarely, a slightly increased risk of gallstone formation has been described.
Diagnosis of the Condition
Gilbert’s Syndrome is often discovered incidentally—for example, during a blood test as part of a routine check-up. It is characterized by an isolated elevated level of unconjugated bilirubin in the blood. Typical liver function tests such as ALT, AST, and gamma-GT remain within normal ranges, which is not indicative of acute liver damage.
Since an elevated bilirubin level can also result from other conditions such as increased blood cell breakdown (hemolysis), doctors usually recommend a complete blood count to rule out this possibility.
If Morbus Meulengracht is suspected, a fasting test is often conducted to confirm the diagnosis. After a short period of fasting, the bilirubin level is measured again. An increase in the level supports the diagnosis. In some cases, niacin (nicotinic acid) is used, which can also temporarily increase bilirubin levels.
In cases of doubt, a genetic test is available. This test specifically looks for the mutation in the UGT1A1 gene responsible for the reduced bilirubin processing. A positive result confirms the diagnosis definitively.
How Is Gilbert’s Syndrome Treated?
The elevated bilirubin level in Morbus Meulengracht does not pose a health risk and generally does not require treatment. However, it is important to be cautious with medications, as certain drugs may be metabolized differently due to the altered liver function and should be monitored by a healthcare professional.
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A Diagnosis That Reassures Rather Than Worries
In general, Gilbert’s syndrome is considered a benign metabolic disorder. The genetic variant does not cause organ damage, so it is not typically referred to as a disease but rather a disorder.
The increased bilirubin concentration even offers several health benefits. Bilirubin acts as a powerful antioxidant, protecting the body from oxidative stress, which is involved in the development of numerous diseases. Studies suggest that affected individuals have a lower risk of cardiovascular diseases, as bilirubin helps protect blood vessels and reduce inflammation.5 There is also a reduced risk for certain types of cancer, such as colon cancer.6
Additionally, individuals with this genetic variant often experience several health benefits. Bilirubin acts as a powerful antioxidant, protecting the body from oxidative stress, which is involved in the development of numerous diseases. Furthermore, they have a lower risk of certain types of cancer, such as colon cancer.