Direct Bilirubin
The portion of bilirubin already processed by the liver and destined for bile.
| Typical reference range | below 0.3 mg/dL |
Ranges vary by laboratory, method, age and sex: always use the range printed on your own report. Why labs differ.
What it measures
Direct (conjugated) bilirubin has been made water-soluble by the liver enzyme UGT1A1. Normally it is excreted promptly into bile, so very little circulates.
Why it matters
An increase in direct bilirubin indicates a problem with the liver's ability to excrete bile or an obstruction of bile flow, rather than increased red cell breakdown.
What a high result can mean
Elevated direct bilirubin suggests bile duct obstruction (gallstones, strictures, tumors), hepatitis, cirrhosis, drug-induced cholestasis or rare inherited disorders such as Dubin-Johnson syndrome.
What a low result can mean
Low or undetectable values are normal.
What affects the result
Usually interpreted with total bilirubin, ALP and GGT. Normal direct bilirubin with high total bilirubin points to an indirect cause such as Gilbert's syndrome or hemolysis. Reference limits vary between 0.2 and 0.4 mg/dL across labs.
Units and conversion
Usually reported in mg/dL.
- From umol/L: multiply by 0.058 to get mg/dL
- From mmol/L: multiply by 58.48 to get mg/dL
Also called on lab reports
Bilirubin, Direct, Bilirubin, Conjugated, D. Bili, Bilirubin Direct, Conjugated Bilirubin, DBIL
Related tests: Liver
This page is educational and does not replace advice from a healthcare professional.