Glossary term
Bilirubin
Part of: Liver Function Tests
- Reading time
- 3 min read
- Last reviewed
- Last reviewed January 1970
- Reading level
- Written in plain English
- Reviewed by
- Reviewed by Medipher Editorial Team
A yellow substance made when old red blood cells are broken down. The liver processes it and removes it in bile.
Medipher explains medical wording in plain English — it does not diagnose or replace a clinician. If this is a medical emergency, call your local emergency number immediately.
Simple visual explanation
What is this?
Bilirubin is a yellow-orange substance made when old red blood cells are broken down. The liver processes it and sends it out of the body in bile, and eventually in stool.
There are two forms — 'unconjugated' (before the liver processes it) and 'conjugated' (after). Some reports show both, which helps identify the source of any increase.
Bilirubin is also what gives bruises their yellow-green colour as they heal.
Why is it important?
High bilirubin can cause jaundice, a visible yellow tinge to the skin or the whites of the eyes.
It helps clinicians spot problems with the liver, bile flow or red blood cell breakdown. Many people with mildly high bilirubin have a harmless inherited condition called Gilbert's syndrome.
Where you'll see it: Liver Function Tests (LFTs).
How doctors use this result
Clinicians may use this result to:
- Look for liver, bile-flow or red-cell breakdown problems.
- Investigate visible jaundice or dark urine.
- Interpret liver function together with ALT, AST and albumin.
- Monitor known liver conditions over time.
What's the normal range?
| Adults (total) | < 21 µmol/L (roughly) |
Ranges vary by laboratory.
Mildly high bilirubin with otherwise normal liver tests is very common and often just reflects Gilbert's syndrome, which needs no treatment.
Normal ranges are guides, not verdicts. Interpretation depends on your age, sex, symptoms, medical history, medications and other investigations — which is why your clinician looks at the whole picture rather than a single value.
Common reasons it may be high
Gilbert's syndrome
A harmless inherited variation slows how the liver processes bilirubin, especially during fasting or illness.
Bile-flow problems
Gallstones or blockages back bilirubin up into the blood.
Liver conditions
A damaged liver can't process bilirubin efficiently.
Increased red-cell breakdown
More red cells being broken down means more bilirubin produced.
Certain medications
Some drugs interfere with bilirubin processing or transport.
Does an abnormal result always mean something is wrong?
Not necessarily. A number that sits outside the printed range is a prompt for interpretation — not a diagnosis.
- A single result rarely gives the full picture — clinicians interpret it alongside your symptoms.
- Your medical history, medications and other blood tests all shape the meaning of one value.
- Small movements just outside the reference range are common and often not concerning.
- Repeat testing over time is frequently more useful than any single number.
What might happen next?
- A repeat blood test.
- Other liver tests (ALT, AST, ALP, albumin) to build a fuller picture.
- Imaging such as ultrasound if bile flow is a concern.
One result rarely tells the whole story. Clinicians look at your symptoms, medical history, medications and other tests together — and a single value that sits slightly outside the reference range is often normal for you. Repeat testing over time is frequently more useful than any one number. Medipher helps you understand what a result means in plain English, but it cannot diagnose medical conditions or replace advice from a doctor, nurse or pharmacist.
When should I speak to a healthcare professional?
Speak with your GP or another healthcare professional if:
- You've been asked to repeat the test.
- You're experiencing new or worsening symptoms.
- Your clinician has flagged the result as needing follow-up.
- You don't understand your results or feel unsure what to do next.
If you have severe symptoms — chest pain, severe breathlessness, fainting, heavy bleeding or feel very unwell — seek urgent help. If this is a medical emergency, call your local emergency number immediately. Medipher is designed to help explain medical information and is not an emergency service.
Frequently asked questions
Related blood tests
Terms clinicians often look at alongside Bilirubin.
- ALTAn enzyme found mainly in liver cells. It leaks into the blood when the liver is irritated or damaged.
- ASTAn enzyme found in the liver, muscle and other tissues. It rises when these tissues are irritated or damaged.
- AlbuminThe main protein in your blood, made by the liver. It helps keep fluid inside your blood vessels.
Related guides
Still unsure what your result means?
This page explains one medical term. If you have a blood test, GP letter or hospital report, Medipher can explain your entire document in plain English.
- what your results mean
- unfamiliar medical terminology
- what your clinician may be monitoring
- useful questions to ask at your next appointment
Sources
General patient information referenced when writing this page.
Was this page helpful?
Help us improve this explanation — your answer is anonymous.
Nearly there — keep going.
A short summary and recommended next reads are just below.
Continue learning
- Next upALTAn enzyme found mainly in liver cells. It leaks into the blood when the liver is irritated or damaged.
- Next upAlbuminThe main protein in your blood, made by the liver. It helps keep fluid inside your blood vessels.
- Next upAnaemiaA condition where you don't have enough healthy red blood cells or haemoglobin to carry oxygen around your body.
This glossary entry is general health information, not medical advice. Medipher explains medical wording in plain English and does not diagnose, provide treatment advice, or replace a GP, doctor, nurse or pharmacist. Always discuss your results with a qualified clinician.