Bilirubin Levels Chart: Newborns, Adults and Age Ranges
Explore a bilirubin levels chart for newborns and adults, understand reference ranges, high bilirubin results and why age affects interpretation.
A bilirubin levels chart is one of the most searched laboratory references in both adult health and newborn care — and one of the most easily misread. Understanding what bilirubin is, why reference ranges differ so significantly between adults and newborns, and why age in hours can be more important than a single numerical value, is essential before drawing any conclusions from a laboratory report.
What is a bilirubin levels chart?
A bilirubin levels chart is a reference table showing the expected or typical range of bilirubin concentrations in blood (or urine), organised by measurement type and patient group. Because interpretation depends on age, gestational age, units of measurement and the specific test used, a single universal chart cannot apply to every individual.
This article provides a structured, evidence-based guide to bilirubin reference ranges for UK adults and newborns, including why these populations require entirely separate approaches to interpretation.
What Is Bilirubin and Why Does It Matter?
Bilirubin is a yellow pigment produced during the normal breakdown of red blood cells. When red blood cells reach the end of their lifespan — typically around 120 days in adults — haemoglobin is released and subsequently broken down into haem. This haem is then converted into bilirubin.
The liver plays a central role in processing bilirubin:
- Unconjugated (indirect) bilirubin — the initial form, which is not water-soluble and travels through the bloodstream bound to albumin.
- Conjugated (direct) bilirubin — once inside the liver, unconjugated bilirubin is chemically modified (conjugated with glucuronic acid) to become water-soluble and is then excreted into bile.
- Total bilirubin — the sum of both conjugated and unconjugated bilirubin, and the most commonly reported measurement in routine laboratory reports.
When bile flow is impaired, when the liver is under stress, or when red blood cells are breaking down faster than normal, bilirubin can accumulate in the blood, causing the yellow colouring of the skin and whites of the eyes known as jaundice.
Why the test type matters: A report showing only total bilirubin gives less information than one that separates direct and indirect fractions. When a result is borderline or abnormal, the pattern of fractions often guides further assessment. Always note the exact test name on your report.
Practical Insight: When reviewing any bilirubin result, identify whether the figure represents total, direct or indirect bilirubin, and whether the units are µmol/L (used by most UK laboratories) or mg/dL (more common in US references). Comparing µmol/L values against mg/dL reference ranges — or vice versa — will give a misleading picture. To convert: 1 mg/dL ≈ 17.1 µmol/L.
Bilirubin Levels Chart for Adults
Commonly Reported Adult Reference Ranges (UK)
Most UK NHS laboratories report total serum bilirubin as part of a liver function test (LFT) panel. The ranges below reflect those published by NHS laboratory services and widely cited UK clinical references, but individual laboratories may use slightly different thresholds depending on their analytical method and equipment.
| Measurement | Typical UK Adult Reference Range (µmol/L) | Approximate Equivalent (mg/dL) |
|---|---|---|
| Total bilirubin | 3 – 21 µmol/L | 0.2 – 1.2 mg/dL |
| Conjugated (direct) bilirubin | < 5 µmol/L | < 0.3 mg/dL |
| Unconjugated (indirect) bilirubin | Calculated; typically < 17 µmol/L | < 1.0 mg/dL |
Source: NHS Lothian Biochemistry Reference Ranges; Daly & Walker, Bilirubin Measurement, in Clinical Biochemistry (2018); Leeds Teaching Hospitals NHS Trust Laboratory Reference Ranges. Values reflect commonly cited adult reference intervals in UK practice.
Important caveats:
- Reference ranges vary between laboratories. Always compare your result against the reference range printed on your own laboratory report.
- Gilbert’s syndrome — a benign, common condition affecting approximately 5–10% of the UK population — can cause mildly raised unconjugated bilirubin (often 20–50 µmol/L) without liver disease.
- Bilirubin levels in adults can fluctuate with fasting, illness, physical exertion and certain medications.
- A result slightly above the upper limit of the reference range is not automatically clinically significant and must be considered alongside the clinical picture.
- Adult reference ranges must not be applied to newborns. Newborn bilirubin physiology and the relevant thresholds are entirely different.
What Affects Adult Bilirubin Interpretation?
- Sex: Some studies suggest marginally higher bilirubin in males, though this does not significantly alter the reference range used in most UK laboratories.
- Age: Bilirubin levels in older adults may be interpreted alongside changes in liver function and red blood cell turnover; however, a separate age-specific adult chart is not routinely applied in UK laboratory practice.
- Fasting state: An overnight fast can raise unconjugated bilirubin, particularly in individuals with Gilbert’s syndrome.
- Haemolysis in the blood sample: Can falsely elevate results.
Bilirubin Levels Chart for Newborns
Why Newborns Are Entirely Different
Newborn bilirubin physiology cannot be assessed using adult reference ranges. Understanding this distinction is critical.
At birth, a newborn rapidly transitions from foetal haemoglobin to adult haemoglobin, causing accelerated breakdown of red blood cells and, consequently, a surge in bilirubin production. At the same time, a newborn’s liver enzyme systems are not yet fully mature, meaning bilirubin conjugation and excretion are less efficient. The result is a predictable, physiological rise in bilirubin during the first days of life.
This is so common that it has a name: physiological jaundice of the newborn. It is estimated to affect up to 60% of term newborns and up to 80% of preterm newborns in the first week of life.
Why a Single “Normal“ Newborn Bilirubin Value Is Misleading
A question frequently asked online is: "What is the normal bilirubin level in neonates?" The honest answer is that there is no single universal value that applies to all newborns. The clinically meaningful threshold depends on:
- Age in hours — bilirubin naturally peaks around 72–96 hours in term babies and then declines; a level of 180 µmol/L at 48 hours carries a different significance than the same level at 120 hours.
- Gestational age — premature babies have lower bilirubin thresholds for clinical concern.
- Risk factors — including blood group incompatibility, bruising, haemolytic conditions, infection and family history.
- Clinical condition — a baby who is feeding poorly, excessively sleepy or showing other signs of illness requires prompt assessment regardless of a single bilirubin value.
NICE Neonatal Jaundice Guidance
In the UK, the assessment of newborn jaundice is guided by NICE Guideline CG98: Neonatal Jaundice (2010, updated 2016). This guideline provides age-specific threshold graphs (in µmol/L) plotted against postnatal age in hours, separately for:
- Term and near-term babies (≥ 38 weeks gestation)
- Babies between 35 and 37 weeks gestation
These graphs — sometimes called the neonatal jaundice bilirubin graph or NICE treatment threshold chart — specify levels at which phototherapy or exchange transfusion should be considered. They are available directly from NICE (nice.org.uk/guidance/cg98) and are used by NHS maternity and neonatal services across the UK.
These thresholds are clinical action thresholds, not simple reference ranges. They are intended for use by healthcare professionals with access to the full clinical picture.
Key point for parents and carers: If you are reviewing a newborn bilirubin result, it is important to ask the clinical team to explain where the level sits on the age-specific chart, taking into account your baby’s exact age in hours, gestational age and any relevant risk factors. A number in isolation, without the chart, is incomplete information.
A Guide to Approximate Bilirubin Rises in Term Newborns
The following figures are illustrative of the typical physiological pattern observed in healthy term newborns. They are not treatment thresholds and should not be used as such.
| Postnatal Age | Typical Total Serum Bilirubin Range (Term Newborns) | Notes |
|---|---|---|
| Day 1 (< 24 hours) | Generally < 100 µmol/L | Jaundice in first 24 hours always requires urgent medical review |
| Day 2–3 (24–72 hours) | Often 100–200 µmol/L | Peak rising phase; clinical action depends on NICE chart |
| Day 3–5 (72–120 hours) | Peak commonly 150–250 µmol/L | Physiological peak in term babies |
| Day 5–14 | Gradual decline | Persistent or worsening jaundice requires assessment |
| > 14 days (term) | Should be declining towards adult range | Prolonged jaundice (> 14 days term, > 21 days preterm) requires investigation |
Source: Adapted from NICE CG98 (2016) and NHS Newborn Blood Spot and Jaundice Screening guidance. These values are indicative of the physiological pattern in healthy term newborns only and must not be used as standalone diagnostic or treatment thresholds.
Premature Babies and Bilirubin: A Separate Assessment
Babies born before 37 weeks of gestation — and particularly those born before 35 weeks — require assessment using different criteria from term-born babies. Premature infants are at greater risk of bilirubin-related harm at lower serum bilirubin concentrations, partly because:
- Their blood-brain barrier is less mature and more permeable
- They are more likely to have lower albumin levels (which binds and transports bilirubin safely)
- Complicating factors such as respiratory distress, infection, acidosis and low blood sugar can increase vulnerability
NICE CG98 provides a separate phototherapy threshold graph for babies between 35 and 37 weeks gestation. For babies born earlier than 35 weeks, specialist neonatal guidelines and clinical judgement are used, as population-specific charts for very preterm infants involve additional complexity.
The important principle: A total serum bilirubin value that falls within the acceptable range for a 40-week baby may be above the action threshold for a 28-week baby. Do not apply a term-infant bilirubin chart to a premature infant.
High Bilirubin Levels: What Can They Indicate?
When bilirubin is elevated above the relevant reference range, this is called hyperbilirubinaemia. The causes differ significantly between adults and newborns.
In Adults
High bilirubin can result from:
- Increased red blood cell breakdown (haemolysis): Conditions such as haemolytic anaemia can produce more bilirubin than the liver can process. Unconjugated bilirubin tends to rise.
- Liver cell dysfunction: Hepatitis (viral, alcoholic or autoimmune), cirrhosis and drug-related liver injury can impair conjugation and excretion of bilirubin. Both fractions may be affected.
- Reduced bile flow (cholestasis): Gallstones, bile duct obstruction or liver conditions affecting bile ducts can cause conjugated bilirubin to accumulate and, in some cases, to spill into the urine.
- Benign conditions: Gilbert’s syndrome is a common, harmless cause of mildly raised unconjugated bilirubin, often noticed incidentally on routine blood tests.
A high bilirubin result alone is not a diagnosis. It is one piece of information within a broader clinical assessment.
In Newborns
The most common cause of raised bilirubin in newborns is physiological jaundice, as described above. However, bilirubin levels that rise too quickly, peak too high or persist too long may reflect:
- Blood group incompatibility (e.g. ABO or Rhesus incompatibility between mother and baby)
- G6PD deficiency — a red blood cell enzyme deficiency more common in certain ethnic backgrounds
- Sepsis (infection)
- Polycythaemia (high red blood cell count)
- Cephalhaematoma or significant bruising from birth trauma
- Breastfeeding jaundice (due to insufficient feeding and dehydration in the early days) or, separately, breast milk jaundice (a more prolonged but usually benign form)
- Hypothyroidism
- Rare metabolic or liver conditions including biliary atresia, which requires urgent investigation if conjugated bilirubin is elevated
Conjugated hyperbilirubinaemia in a newborn (where conjugated bilirubin is > 25 µmol/L or > 20% of total bilirubin) is always abnormal and requires urgent specialist assessment. This is distinct from the unconjugated jaundice that characterises physiological newborn jaundice.
What Does a Result Within the Normal Range Mean?
A bilirubin result that falls within the laboratory’s stated reference range generally suggests that, for this particular measurement, no significant abnormality is detected. However:
- A result within the reference range does not rule out every possible liver or blood condition.
- Context matters: symptoms, other blood test results, medication history and clinical examination all contribute to the overall picture.
- The pattern of bilirubin fractions (total, direct and indirect) often provides more information than total bilirubin alone.
- Reference ranges describe the statistical distribution of values in a healthy population. A small proportion of healthy people will have values outside the reference range, and a small proportion of people with a condition will have values within it.
For the keyword searches around jaundice normal value and bilirubin chart, the key takeaway is this: a reference range is a starting point for interpretation, not a definitive answer.
Blood Bilirubin vs Urine Bilirubin
Searches for a urine bilirubin levels chart are common, and it is important to clarify why blood and urine bilirubin results cannot be directly compared using the same reference values.
- Blood (serum) bilirubin is measured in µmol/L or mg/dL and reflects the total concentration of bilirubin in the circulation.
- Urine bilirubin is typically detected using a urine dipstick and is reported qualitatively (negative, trace, 1+, 2+, 3+) rather than as a precise concentration.
Normally, bilirubin is absent from urine in healthy adults, because unconjugated bilirubin is not water-soluble and cannot be filtered by the kidneys. Conjugated (direct) bilirubin is water-soluble and can appear in urine when levels in the blood are elevated — typically in conditions affecting bile flow or liver cell function.
A positive urine bilirubin on a dipstick is a sign that warrants further investigation, but it does not translate directly to a specific serum bilirubin value. The two tests measure different things in different ways, and urine dipstick bilirubin thresholds cannot be read against a serum bilirubin reference range.
When Should Bilirubin Results Be Reviewed by a Healthcare Professional?
For Newborns and Their Parents
- Jaundice appearing within the first 24 hours of life requires urgent medical assessment — this is not physiological jaundice and always needs prompt evaluation.
- Bilirubin results in newborns should be reviewed against an age-specific and gestational-age-specific chart by a healthcare professional with access to the full clinical picture.
- Contact your midwife, health visitor or GP promptly if your baby appears more yellow, is difficult to feed, is unusually sleepy, difficult to rouse, or is not producing wet nappies.
- Seek urgent care if jaundice is worsening rapidly, your baby has a high-pitched cry, is very floppy or you are concerned about their wellbeing.
- Jaundice persisting beyond 14 days in a term baby (21 days in a preterm baby) should always be assessed by a healthcare professional to rule out conditions such as biliary atresia, which requires early treatment.
This article and any private laboratory bilirubin test are not appropriate substitutes for clinical newborn jaundice assessment. Private blood testing does not provide the clinical context, age-specific graphing or professional assessment required to manage neonatal jaundice safely.
For Adults
- Yellowing of the skin or whites of the eyes (scleral icterus) should be assessed by an appropriate healthcare professional, particularly when accompanied by dark urine, pale stools, abdominal pain, unexplained weight loss, fatigue or nausea.
- A mildly raised bilirubin on a routine blood test, without symptoms and with otherwise normal liver function results, may reflect something benign such as Gilbert’s syndrome — but this should be confirmed by a clinician.
- If you have received a liver function test result and have questions about what it means, your GP is the appropriate first point of contact.
If you are interested in understanding your routine blood test results more broadly or exploring preventive testing, an affordable private health check in London can help you establish a baseline picture of your general health markers.
Frequently Asked Questions
1. What is a bilirubin levels chart?
A bilirubin levels chart is a reference guide showing expected bilirubin concentrations in blood, organised by measurement type (total, direct or indirect), patient group (adult or newborn) and units. Because normal ranges differ significantly between adults and newborns — and because newborn thresholds change hour by hour — no single chart applies universally. Always compare any result against the reference range specific to the relevant population, laboratory and age group.
2. What is a normal bilirubin level in adults in the UK?
Most UK NHS laboratories report a total serum bilirubin reference range of approximately 3–21 µmol/L (roughly 0.2–1.2 mg/dL) for adults, with conjugated (direct) bilirubin typically below 5 µmol/L. However, individual laboratories may use slightly different thresholds depending on their methods and equipment. Always refer to the reference range printed on your own laboratory report, rather than comparing against a generic online value.
3. Are newborn bilirubin levels different from adult levels?
Yes — significantly so. Newborns experience a predictable, physiological rise in bilirubin in the first days of life as foetal haemoglobin breaks down and the liver matures. Total bilirubin can rise well above adult reference ranges without causing harm in a healthy term newborn. However, the appropriate threshold depends on the baby’s age in hours, gestational age and risk factors. Adult reference ranges cannot be applied to newborns.
4. How does a bilirubin level chart by age work?
In adults, age has a relatively minor effect on bilirubin interpretation, and most UK laboratories use a single reference range across the adult population. In newborns, age in hours is fundamental — the same bilirubin value at 24 hours carries a different significance than at 96 hours. Clinical bilirubin charts for newborns plot serum bilirubin against postnatal age in hours, with phototherapy thresholds rising and then falling across the first week.
5. What can high bilirubin levels mean?
In adults, raised bilirubin may reflect increased red blood cell breakdown (haemolysis), reduced liver function, impaired bile flow or a benign condition such as Gilbert’s syndrome. In newborns, physiological jaundice is the most common cause, but higher levels or rapid rises may indicate blood group incompatibility, infection, G6PD deficiency or, in cases where conjugated bilirubin is raised, a liver or bile duct problem requiring urgent assessment. A high result alone is not a diagnosis.
6. Why is a bilirubin chart for premature babies different?
Premature infants have less mature blood-brain barriers, lower albumin levels and more complex clinical conditions, which means they may be harmed by bilirubin levels that would be considered acceptable in a term baby. NICE provides separate threshold graphs for babies between 35 and 37 weeks gestation. For those born earlier than 35 weeks, specialist neonatal clinical guidelines and individual clinical assessment are used. Never apply a term-infant bilirubin chart to a premature baby.
7. What is the difference between total and direct bilirubin?
Total bilirubin is the sum of all bilirubin in the blood — both the unconjugated (indirect) form and the conjugated (direct) form. Direct bilirubin refers specifically to conjugated bilirubin, which has been processed by the liver and is water-soluble. Indirect bilirubin is usually calculated as total minus direct. The pattern of these fractions helps identify whether an abnormal result is more likely to reflect a problem with bilirubin production, liver processing or bile excretion.
8. Can urine bilirubin results be compared with blood bilirubin results?
No — they are not directly comparable. Blood (serum) bilirubin is measured as a precise concentration (µmol/L or mg/dL), whereas urine bilirubin from a dipstick test is reported qualitatively (negative, trace or 1+ to 3+). Normally, no bilirubin should appear in urine. Its presence suggests that conjugated bilirubin is elevated in the blood, but urine dipstick results cannot be read against a serum bilirubin reference range.
9. Does a high bilirubin result always mean liver disease?
Not always. Gilbert’s syndrome, a common and benign genetic variant affecting 5–10% of the population, causes mildly raised unconjugated bilirubin without liver damage. Haemolysis (increased red blood cell breakdown) can also raise bilirubin without primary liver disease. Conversely, liver disease does not always produce a strikingly elevated bilirubin in the early stages. A bilirubin result should be considered alongside the full liver function panel, clinical symptoms and other relevant investigations.
10. When should newborn jaundice be assessed?
Any jaundice appearing within the first 24 hours of life requires urgent medical assessment. Jaundice that appears after the first 24 hours and seems mild in a well, feeding baby may be physiological, but it still requires monitoring and measurement against an age-specific chart. Parents should seek prompt medical advice if jaundice is worsening, their baby is difficult to feed, unusually sleepy or not producing wet nappies. Jaundice lasting beyond 14 days (term) or 21 days (preterm) always needs professional evaluation.
Understanding Your Results Further
If you are an adult who has received a bilirubin result as part of a routine blood test panel, understanding the broader context of your liver function and metabolic health can be valuable. A full health screening package may include liver function tests alongside other metabolic and cardiovascular markers, helping to build a more complete picture of your health.