Direct (Conjugated) Bilirubin Unit Converter
Direct (Conjugated) Bilirubin Unit Converter
Convert direct bilirubin between mg/dL, µmol/L, mg/L and µg/dL, and see whether the fraction points to a cholestatic cause.
Direct (Conjugated) Bilirubin converter
Mass ⇄ molarDirect bilirubin 0.6 mg/dL with a total of 1.4 mg/dL
Formula and conversion factor
Conjugated fraction (%) = direct ÷ total × 100
- 17.104
- from the molecular weight of bilirubin, 584.66 Da
- > 20%
- a conjugated fraction above this points to hepatocellular or cholestatic disease
- delta bilirubin
- albumin-bound conjugated bilirubin that persists after obstruction resolves, and is measured within the direct fraction
Worked example
Direct bilirubin 0.6 mg/dL with a total of 1.4 mg/dL
0.6 × 17.104 = 10.3 µmol/L
Conjugated fraction = 0.6 ÷ 1.4 = 43% → conjugated pattern
Interpreting the fraction
| Conjugated fraction | Pattern | Consider |
|---|---|---|
| < 20% | Unconjugated | Haemolysis, Gilbert syndrome, haematoma resorption |
| 20 – 50% | Mixed | Hepatocellular disease |
| > 50% | Conjugated | Biliary obstruction, cholestasis, Dubin-Johnson, Rotor |
Why the fraction matters
Direct bilirubin is measured by its reaction with diazo reagent without an accelerator, and it approximates the conjugated fraction — the bilirubin that has already been processed by hepatocytes and is water-soluble. The distinction from total bilirubin is what turns a single number into a diagnostic direction.
An elevated conjugated fraction means bilirubin has been conjugated but not excreted, which localises the problem to the hepatocyte’s excretory step or to the biliary tree beyond it. Obstruction, drug-induced cholestasis, hepatitis, sepsis and the rare hereditary disorders Dubin-Johnson and Rotor all produce this pattern. Unlike unconjugated elevation, it has no benign familial explanation, so it always warrants investigation — in practice an ultrasound first.
In neonates the same principle carries much greater urgency. Unconjugated jaundice is expected in the first days of life; conjugated jaundice never is. A direct bilirubin above 1 mg/dL, or above 20% of the total, in a jaundiced infant demands immediate assessment for biliary atresia, where the outcome of the Kasai procedure depends heavily on operating before about eight weeks of age.
Frequently asked questions
Is direct bilirubin the same as conjugated bilirubin?
Almost. Direct bilirubin is what the diazo reaction measures without an accelerator, and it includes conjugated bilirubin plus delta bilirubin, the albumin-bound form. The terms are used interchangeably in practice.
What conjugated fraction is significant?
Above 20% of the total suggests a hepatocellular or cholestatic process. Below 20% points to an unconjugated cause such as haemolysis or Gilbert syndrome.
Why does conjugated jaundice matter more in newborns?
Unconjugated jaundice is physiological in the first days of life; conjugated jaundice never is. It requires urgent assessment for biliary atresia, where surgical outcome depends on early intervention.
What is delta bilirubin?
Conjugated bilirubin covalently bound to albumin. Because it shares albumin’s long half-life it persists for weeks after an obstruction resolves, which explains a slowly falling direct bilirubin in a recovering patient.
Related calculators
References
- Fevery J. Bilirubin in clinical practice: a review. Liver Int. 2008;28(5):592–605.
- NICE guideline NG144 — jaundice in newborn babies under 28 days.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.