What It Means When Your Bilirubin Is Low

Bilirubin, a yellow pigment found in bile, is created by the breakdown of red blood cells and helps to digest your food, per the Cleveland Clinic. Due to its antioxidant and anti-inflammatory effects, this compound also protects against free radical damage and certain diseases, according to a 2009 review published in Revista Colombiana de Gastroenterología. As the researchers note, bilirubin has greater antioxidant activity than vitamin E and a stronger cardioprotective effect than high-density lipoprotein (HDL) — the "good" cholesterol. What's more, people with slightly higher bilirubin levels may be at lower risk for peripheral artery disease than those with normal levels, suggests the above review. However, elevated bilirubin can also be a sign of liver disease or red blood cell disorders, warns the Cleveland Clinic.

Having low bilirubin levels may also seem concerning, even if you have no other symptoms. But what does it mean when your bilirubin is low? Should you be concerned about your liver or other vital organs? Let's see what the research says. 

Potential causes of low bilirubin levels

Your doctor might suggest a blood test if they suspect an issue with your bilirubin levels. A bilirubin test will show different values, including direct or conjugated bilirubin, and total bilirubin (per Icahn School of Medicine at Mount Sinai). Direct bilirubin levels should be less than 0.3 milligrams per deciliter, whereas total bilirubin shouldn't exceed 0.1 to 1.2 milligrams per deciliter. These values may be lower than normal due to caffeine consumption or certain medications, such as barbiturates and non-steroidal anti-inflammatory drugs, notes Healthline. That being said, low bilirubin levels, or hypobilirubinemia, isn't usually a cause for concern.

However, some studies suggest that having lower-than-normal bilirubin levels could make you vulnerable to a range of health issues. For example, a recent review featured in the American Journal of Physiology-Endocrinology and Metabolism found a potential link between hypobilirubinemia and coronary artery disease, heart attack, stroke, metabolic syndrome, and diabetes. Moreover, low bilirubin levels may increase the risk of non-alcoholic fatty liver disease, sleep apnea, and kidney disorders.

These associations may be due to the antioxidant and anti-inflammatory effects of bilirubin, says Healthline. If your body doesn't produce enough of it, you may not benefit from the same protection against oxidative stress and inflammation as someone with normal bilirubin levels. But even so, there's not enough evidence to confirm a causal association between hypobilirubinemia and human disease. The best thing you can do is discuss these aspects with your doctor and undergo further testing if needed.