What is the significance of a total bilirubin level of 12 micromoles per liter (umol/L), with a reference range of less than 20 micromoles per liter (umol/L)?

From the Guidelines

The total bilirubin level of 12 umol/L is within the normal range, and therefore, no medical intervention is required for this result. Bilirubin is a by-product of the breakdown of haemoglobin by the reticuloendothelial system, and it exists in two forms, unconjugated and conjugated, as stated in the guidelines on the management of abnormal liver blood tests 1. The fact that the total bilirubin level is 12 umol/L, which is below the reference range of less than 20 umol/L, indicates that the liver is functioning properly in terms of processing and excreting bilirubin.

Some key points to consider when interpreting bilirubin levels include:

• The majority of measurable bilirubin should be conjugated, even in individuals with significant liver disease, as noted in the guidelines 1
• Elevations of either the unconjugated or conjugated fraction will lead to a rise in the measured bilirubin concentration
• Gilbert’s syndrome, an inherited disorder of metabolism, is the most common cause of an isolated elevated bilirubin concentration, but this is not relevant in this case since the bilirubin level is within the normal range

Given that the total bilirubin level is normal, it suggests healthy liver function and normal red blood cell turnover. This test result is reassuring and doesn't require any follow-up unless you have other concerning symptoms or abnormal liver function tests. It's essential to consider other liver function tests, such as albumin, prothrombin time (PT), and INR, to get a comprehensive picture of liver health, as these tests can provide additional information on the liver's synthetic function and potential liver injury 1.

From the Research

Bilirubin Levels and Ursodeoxycholic Acid

• The patient's total bilirubin level is 12 umol/L, which is within the reference range of <20 umol/L.
• Studies have shown that ursodeoxycholic acid (UDCA) can improve liver function and reduce bilirubin levels in patients with liver disease 2, 3, 4, 5, 6.
• A study published in 2023 found that UDCA improved liver function tests, including total bilirubin, in living liver donors after hepatectomy 4.
• Another study published in 2018 found that UDCA was more effective than phenobarbital in reducing direct bilirubin levels in neonates and young infants with cholestasis 3.
• A study published in 1999 found that UDCA treatment was associated with improved serum liver tests, including bilirubin, in patients with primary biliary cirrhosis 5.
• A study published in 1989 found that UDCA administration reduced serum bilirubin levels in patients with chronic liver disease, particularly in those with primary biliary cirrhosis 6.

Ursodeoxycholic Acid Dosage and Efficacy

• The optimal dosage of UDCA for improving liver function and reducing bilirubin levels is not well established, but studies have used dosages ranging from 250 to 750 mg/day 6.
• A study published in 1989 found that a dosage of 250 mg/day was effective in reducing serum enzyme levels and bilirubin in patients with chronic liver disease 6.
• Higher dosages of UDCA may be more effective in improving liver function, but the benefits and risks of higher dosages need to be carefully evaluated 6.

Clinical Implications

• The use of UDCA may be beneficial in patients with liver disease, particularly those with elevated bilirubin levels 2, 3, 4, 5, 6.
• Further studies are needed to determine the optimal dosage and duration of UDCA treatment for improving liver function and reducing bilirubin levels in patients with liver disease.