Bilirubin mg/dL to µmol/L Converter

Bilirubin in two units: the short answer

To convert bilirubin from mg/dL to µmol/L, multiply by 17.1. To convert µmol/L back to mg/dL, divide by 17.1 (or multiply by 0.0585). A total bilirubin of 1.0 mg/dL is therefore 17 µmol/L, and 50 µmol/L is 2.9 mg/dL. The converter above handles both directions and shows the typical adult range and the level at which jaundice usually becomes visible.

Bilirubin appears on almost every liver function panel and is the test used to monitor jaundice in newborn babies. The conversion is straightforward, but the stakes can be high: newborn treatment charts, liver disease scores and drug-dosing rules are often written in only one unit, and mixing them up can make a dangerous level look safe or a normal level look alarming. This guide explains the conversion, the different bilirubin fractions, normal ranges, the causes of a raised bilirubin, and the special case of newborn jaundice.

What bilirubin is

Bilirubin is a yellow-orange pigment produced when heme – the iron-containing part of hemoglobin – is broken down. Each day, roughly 1% of red blood cells reach the end of their lifespan of about 120 days and are removed, mainly in the spleen. Their heme is converted first to biliverdin and then to bilirubin. About 80% of bilirubin comes from old red cells; the rest comes from other heme-containing proteins such as myoglobin and cytochromes.

The pathway then has three stages:

1. Transport. Newly formed bilirubin is not water-soluble. It travels in the blood tightly bound to albumin. This is called unconjugated or indirect bilirubin.
2. Conjugation. In the liver, the enzyme UGT1A1 attaches glucuronic acid to bilirubin, making it water-soluble. This is conjugated bilirubin.
3. Excretion. Conjugated bilirubin is secreted into bile, flows into the intestine, and is converted by gut bacteria into urobilinogen and stercobilin, which give stools their brown colour. Some urobilinogen is reabsorbed and excreted in urine.

A problem at any of these stages can raise bilirubin, and identifying which stage is affected is the key to working out the cause.

mg/dL and µmol/L explained

• mg/dL (milligrams per deciliter) – used in the United States and some other countries.
• µmol/L (micromoles per liter) – the SI unit, used in the UK, Europe, Canada, Australia and elsewhere.

Why the factor is 17.1

Bilirubin has a molar mass of 584.7 g/mol. A concentration of 1 mg/dL is 10 mg per liter, or 10,000 µg per liter, which is 10,000 ÷ 584.7 = 17.1 µmol/L. Conversely, 1 µmol/L = 0.0585 mg/dL.

How to convert bilirubin step by step

1. Check the unit and whether the result is total, direct (conjugated) or indirect (unconjugated) bilirubin.
2. For mg/dL to µmol/L, multiply by 17.1.
3. For µmol/L to mg/dL, divide by 17.1.
4. Round µmol/L to whole numbers and mg/dL to one decimal place.

Worked examples

• 0.3 mg/dL × 17.1 = 5 µmol/L.
• 1.2 mg/dL × 17.1 = 21 µmol/L – the upper end of a typical adult range.
• 2.5 mg/dL × 17.1 = 43 µmol/L – roughly where jaundice becomes visible in adults.
• 5.0 mg/dL × 17.1 = 86 µmol/L.
• 15 mg/dL × 17.1 = 257 µmol/L – a level relevant to phototherapy decisions in newborns.
• 34 µmol/L ÷ 17.1 = 2.0 mg/dL.
• 300 µmol/L ÷ 17.1 = 17.5 mg/dL.

Mental shortcut

Multiply mg/dL by 17, or divide µmol/L by 17. For 3.0 mg/dL: 3 × 17 = 51 µmol/L (exact: 51.3).

Bilirubin conversion chart

Normal bilirubin ranges

Typical adult reference ranges are about:

• Total bilirubin: 0.1–1.2 mg/dL (2–21 µmol/L). Many UK laboratories use an upper limit of about 21 µmol/L.
• Direct (conjugated) bilirubin: below about 0.3 mg/dL (5 µmol/L).
• Indirect (unconjugated) bilirubin: total minus direct, typically 0.2–0.8 mg/dL (3–14 µmol/L).

Men tend to have slightly higher bilirubin than women. Ranges vary by laboratory and method.

Direct, indirect and conjugated: a note on terms

"Direct" bilirubin is named after the laboratory reaction in which it reacts directly with the test reagent. It mainly reflects conjugated bilirubin but also includes delta bilirubin, a form bound covalently to albumin that persists in the blood for about three weeks. This explains why bilirubin can stay raised for some time after a blockage of the bile duct has been relieved. "Indirect" bilirubin is calculated as total minus direct and approximates unconjugated bilirubin.

Causes of a raised bilirubin

Causes are grouped by which fraction is raised.

Mainly unconjugated (indirect) bilirubin

• Gilbert syndrome – by far the most common cause in otherwise healthy adults. It affects about 5–10% of people of European descent and reflects reduced UGT1A1 activity due to a common genetic variant. Bilirubin is mildly raised, usually below about 3–4 mg/dL (50–70 µmol/L), and typically rises with fasting, illness, stress and dehydration. Liver enzymes are normal. It is harmless and needs no treatment, although it can affect the processing of a few medicines, such as irinotecan.
• Haemolysis – increased breakdown of red cells, for example in hereditary spherocytosis, sickle cell disease, G6PD deficiency, autoimmune haemolytic anaemia, or after a large bruise or haematoma.
• Ineffective red cell production – in severe B12 or folate deficiency or thalassaemia.
• Medicines – rifampicin, some HIV protease inhibitors (atazanavir, indinavir) and others can raise unconjugated bilirubin.
• Crigler–Najjar syndrome – rare, severe inherited UGT1A1 deficiency.

Mainly conjugated (direct) bilirubin

• Liver disease – hepatitis (viral, alcoholic, autoimmune or drug-induced), cirrhosis, fatty liver disease with inflammation.
• Bile duct obstruction – gallstones in the common bile duct, pancreatic cancer, bile duct cancer, strictures.
• Cholestatic liver disease – primary biliary cholangitis, primary sclerosing cholangitis, cholestasis of pregnancy, drug-induced cholestasis.
• Sepsis and severe illness.
• Rare inherited conditions such as Dubin–Johnson and Rotor syndromes.

When conjugated bilirubin is raised, it spills into urine, making it dark ("tea-coloured"), and when bile flow is blocked, stools become pale and itching is common.

Jaundice

Jaundice – yellowing of the skin and the whites of the eyes – usually becomes visible when total bilirubin exceeds about 2.5–3 mg/dL (43–51 µmol/L) in adults, although this varies with skin tone and lighting. The whites of the eyes (sclerae) are usually the first place it is seen. In newborns, jaundice is visible at higher levels, typically above about 5 mg/dL (85 µmol/L), and spreads from the head downwards as levels rise.

Newborn jaundice

Most newborns develop some jaundice in the first week of life, because they have a high red cell mass with a shorter red cell lifespan, and their liver's conjugating enzymes are not yet mature. This physiological jaundice typically peaks on days 3–5 and fades within two weeks.

Very high unconjugated bilirubin can cross into the brain and cause kernicterus, a rare but devastating form of brain damage. To prevent it, newborn bilirubin is measured (with a skin meter or blood test) and plotted on charts that take the baby's age in hours and gestational age into account:

• The American Academy of Pediatrics 2022 guideline provides phototherapy and exchange-transfusion thresholds in mg/dL by hour of age, gestational age and the presence of neurotoxicity risk factors. Thresholds rise over the first days of life and are lower for babies born earlier and for those with risk factors such as haemolysis, sepsis or low albumin.
• NICE guidance (CG98) in the UK provides treatment threshold graphs in µmol/L. For example, for a baby of 38 weeks or more, the phototherapy threshold rises from about 100 µmol/L (5.8 mg/dL) at birth to 350 µmol/L (20.5 mg/dL) from 96 hours of age.

Because these charts are written in different units, converting correctly is essential when families or clinicians compare advice from different countries. Treatment decisions must always be made by the baby's healthcare team using the appropriate chart.

Prolonged jaundice in babies

Jaundice that lasts beyond 14 days in a term baby (21 days in a preterm baby) needs a measurement of conjugated bilirubin. A conjugated bilirubin above about 1.0 mg/dL (17–25 µmol/L, depending on guidance), or above 20% of total, suggests cholestasis and needs urgent assessment for conditions such as biliary atresia, where early surgery greatly improves outcomes. Pale stools or dark urine in a jaundiced baby are warning signs.

Bilirubin in liver disease scores

Bilirubin is part of several scores used to assess the severity of liver disease:

• MELD score (Model for End-Stage Liver Disease), used to prioritise liver transplantation, uses bilirubin in mg/dL. Laboratories reporting in µmol/L must divide by 17.1 before calculation.
• Child–Pugh score awards points for bilirubin bands of below 2 mg/dL (34 µmol/L), 2–3 mg/dL (34–50 µmol/L) and above 3 mg/dL (50 µmol/L).
• Drug-induced liver injury assessment uses Hy's law: a rise in ALT above three times the upper limit together with bilirubin above twice the upper limit indicates a high risk of serious liver injury.

Reading bilirubin with the other liver tests

Bilirubin is most useful when interpreted together with the liver enzymes on the same panel. Common patterns include:

In a person with an isolated mild rise in bilirubin, normal liver enzymes and a normal blood count, Gilbert syndrome is by far the most likely explanation. The ACG guideline suggests confirming that the rise is mainly unconjugated and that there is no evidence of haemolysis; genetic testing is rarely needed.

Bilirubin in pregnancy

Bilirubin can rise in several pregnancy-related liver conditions. Intrahepatic cholestasis of pregnancy, which causes intense itching (often of the palms and soles) in the third trimester, is diagnosed mainly by raised bile acids; bilirubin is raised in only a minority. Acute fatty liver of pregnancy and HELLP syndrome (haemolysis, elevated liver enzymes and low platelets) are rarer but serious conditions in which bilirubin is often raised and urgent obstetric care is needed. Mild unconjugated rises from Gilbert syndrome can also become more noticeable in pregnancy, especially with vomiting.

Bilirubin as an antioxidant

Bilirubin is not only a waste product. In laboratory studies it acts as a powerful antioxidant, and large population studies have found that people with mildly higher bilirubin, including those with Gilbert syndrome, tend to have a lower risk of cardiovascular disease. Whether this is cause and effect is not established, and there is no recommendation to raise bilirubin deliberately.

What affects bilirubin results

• Fasting – raises unconjugated bilirubin, especially in Gilbert syndrome; a 24–48-hour fast can double it.
• Light exposure – bilirubin breaks down in light, so samples should be protected and processed promptly; prolonged exposure can give falsely low results.
• Haemolysis in the sample can interfere with some methods.
• Medicines – many can raise bilirubin, including rifampicin, atazanavir, some antibiotics, anabolic steroids and some chemotherapy.
• Exercise and illness – strenuous exercise and intercurrent illness can raise bilirubin in people with Gilbert syndrome.

Comparing bilirubin results across laboratories

Bilirubin methods are well standardised, so differences between laboratories are usually small. When converting, the main risks are mixing up total and direct bilirubin and forgetting the unit. For example, a person with Gilbert syndrome may have 2.4 mg/dL in the US after a period of fasting and 22 µmol/L in the UK when well. Converted, these are 41 µmol/L and 1.3 mg/dL – a typical fluctuation for Gilbert syndrome, not a sign of new liver disease, provided the liver enzymes remain normal.

Urine bilirubin and urobilinogen

Urine dipsticks can detect bilirubin and urobilinogen. Bilirubin in urine indicates raised conjugated bilirubin (because only conjugated bilirubin is water-soluble), pointing to liver disease or bile duct obstruction. It is absent in Gilbert syndrome and haemolysis. Urobilinogen increases with haemolysis and some liver diseases, and is absent when the bile duct is completely blocked. Dipstick results are qualitative and are not converted between units.

When to see a doctor

See a doctor if you notice yellowing of the skin or eyes, dark urine, pale stools or persistent itching, or if a blood test shows a raised bilirubin with abnormal liver enzymes. Seek urgent care for jaundice with fever and abdominal pain (possible bile duct infection), confusion, vomiting blood or severe drowsiness. For babies, contact a midwife, health visitor or doctor promptly if jaundice appears in the first 24 hours, spreads below the chest, persists beyond two weeks, or the baby is sleepy, feeding poorly, or has pale stools or dark urine.