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Liver

Total bilirubin and fasting: why the level typically rises in Gilbert's syndrome

Bilirubin is a breakdown product of red blood cells that, according to MedlinePlus Genetics, the body can only excrete after an enzyme in the liver cells has attached glucuronic acid to it. According to MedlinePlus Genetics, that attachment makes bilirubin dissolve in water, so that the body can get rid of it.

When that enzyme works more slowly, as in Gilbert's syndrome, unconjugated bilirubin builds up in the blood according to MedlinePlus Genetics. According to MedlinePlus, a high bilirubin can also fit liver disease, a blocked bile duct or anaemia from red blood cells being broken down too fast. Only a blood test shows the level of bilirubin.

Diagnostiek voor U gives 3 to 20 µmol/L for everyone older than 5 days. According to MedlinePlus Genetics, a slightly raised level after a period of fasting fits Gilbert's syndrome.

Doctor's Assessment Included

Bilirubin is the yellow breakdown product of red blood cells, which the liver processes and removes through the bile. For adults, Star-SHL and Certe use an upper limit of 24 µmol/l for men and 19 for women, Unilabs and Diagnostiek voor U 20 for everyone.

  • Total bilirubin is the sum of an unprocessed (indirect) form and a form processed by the liver (direct); a raised unprocessed form is usually due to red cell breakdown or Gilbert's syndrome, a raised processed form usually to liver disease or blocked bile ducts.
  • For an isolated raised bilirubin, with otherwise normal liver tests, the British Society of Gastroenterology (BSG) advises repeating the liver tests on a fasting sample, with a full blood count and direct and indirect bilirubin; in Gilbert's syndrome, total bilirubin then rises further.
  • A bilirubin result depends strongly on the measuring method, which is why limits differ between laboratories.

Reference Ranges

See the value that applies to you:

Choose male or female — this range differs by sex.

Enter your age — this range changes with age.

This range also depends on context such as cycle phase or sample material; the highlighted rows apply to your group.

Your reference range
umol/l
2 29 umol/l
Reference ranges by group, in umol/l
Male · 1–5 years 2–11 umol/l
2 11
Male · 6–12 years 3–16 umol/l
3 16
Male · 13–18 years 4–29 umol/l
4 29
Male · 19 years and older 4–24 umol/l
4 24
Female · 1–5 years 2–10 umol/l
2 10
Female · 6–12 years 3–16 umol/l
3 16
Female · 13–18 years 3–22 umol/l
3 22
Female · 19 years and older 3–19 umol/l
3 19
2 29 umol/l

Source: NVKC Reference population: Dutch general-practice population (NUMBER, n = 7,574,327)

Reference ranges may vary between laboratories. When you order a test, a BIG-registered doctor assesses your personal results in context. For treatment decisions, discuss your results with your GP.

Check your own value

Bilirubin (Total): what Dutch laboratories use

Reference ranges by group, in umol/l
Star-shl · Male · 19 years and older 4–24 umol/l
4 24
Star-shl · Female · 19 years and older 3–19 umol/l
3 19
Unilabs · Everyone · 0–115 years 3–20 µmol/l
3 20
Certe · Male · 18 years and older · a limit, not a range < 24 umol/L
24
Certe · Female · 18 years and older · a limit, not a range < 19 umol/L
19
Diagnostiek voor U · Everyone · 0 years and older 3–20 µmol/L
3 20
0 26.4 umol/l

Source: Star-shl

Source: Unilabs

Source: Certe

Source: Diagnostiek voor U

Each value as the laboratory itself publishes it, retrieved in 2026.

Bilirubin (Total): what this test measures

According to the BSG, the British Society of Gastroenterology, the total bilirubin measurement gives the unconjugated and the conjugated form together, in micromoles per litre (µmol/l). According to MedlinePlus Genetics, in Gilbert's syndrome it is mainly the unconjugated part that is raised.

Diagnostiek voor U notes that the blood sample is sensitive to light, and Unilabs asks for the tube to be protected from light.

Bilirubin (Total): why this value matters

Because Gilbert's syndrome is not linked to liver disease according to the BSG, it matters for a raised total bilirubin whether the syndrome is the cause or liver disease, which according to the BSG develops silently.

According to the BSG, Gilbert's syndrome is the most common cause of an isolated raised bilirubin, and according to the BSG it affects 5 to 8% of the population. According to MedlinePlus Genetics, people with the syndrome have about 30% of the normal function of the enzyme that converts bilirubin.

Bilirubin (Total): how the blood test works

Referral
No GP referral needed. After the order we arrange the referral through ZorgDomein, within one business day; orders after 17:00 or at the weekend start on the next business day. ZorgDomein emails a barcode, and that barcode is what the draw site needs.
The draw
A blood draw from a vein in the arm, at a partner laboratory's draw site. No home kit, no finger prick.
Which test
GLP-1 Baseline Panel · €214,-
Where
650+ draw sites run by independent laboratories across the Netherlands. Draw sites

Bilirubin (Total): when is testing worthwhile?

For the BSG, an isolated raised bilirubin is a reason to repeat the liver tests, this time on blood taken while fasting. In Gilbert's syndrome, according to the BSG, total bilirubin should then rise further, because of the indirect form, with no signs of anaemia.

Apart from Gilbert's syndrome, a doctor may also ask for several hours without food or drink before a bilirubin test, according to MedlinePlus.

Bilirubin (Total): symptoms of a high or low value

Low Levels

Diagnostiek voor U sets the lower limit of total bilirubin for everyone older than 5 days at 3 µmol/L. According to MedlinePlus, a low level can come from medicines such as birth control pills, antibiotics or sleeping pills, but it is usually not a cause for concern.

High Levels

Long periods without food are, according to MedlinePlus Genetics, one of the stresses with which bilirubin typically rises in Gilbert's syndrome, alongside dehydration, illness, vigorous exercise and menstruation. According to MedlinePlus, certain foods are also on the list of things that can give a higher bilirubin, as are some medicines.

Jaundice, yellow skin and yellow eyes, can arise according to MedlinePlus when liver disease or a blocked bile duct makes bilirubin rise. Dark urine, clay-coloured stools and stomach pain are further symptoms that MedlinePlus lists as reasons a doctor may order the test.

Bilirubin (Total): causes of a low or high value

What lowers the value

  • Certain medicines

    A low bilirubin is usually not a cause for concern, but may be due to medicines such as antibiotics, birth control pills, sleeping pills and medicines for seizures.

What raises the value

  • Gilbert's syndrome

    The most common cause of an isolated raised bilirubin is Gilbert's syndrome, an inherited trait that 5 to 8 percent of people have and that is not linked to liver disease.

  • Breakdown of red blood cells

    A slightly raised bilirubin is found when red blood cells break down, as in haemolytic anaemia, and with large bruises.

  • Liver disease

    Hepatitis, damage to the liver tissue, long-term alcohol use or poisoning by medicines can raise bilirubin.

  • Blocked bile ducts

    Gallstones, a tumour of the bile ducts or pancreatic cancer that blocks the flow of bile can raise bilirubin.

  • Strenuous exercise

    Bilirubin can rise after strenuous exercise.

Bilirubin (Total): lifestyle and this value

A raised bilirubin result is one for the GP, together with how long before the blood draw nothing was eaten. According to the BSG, someone with Gilbert's syndrome should be fully reassured. According to MedlinePlus, a doctor who suspects liver disease or a red blood cell disorder may ask for further tests, such as an ultrasound or other liver function tests.

Bilirubin (Total): frequently asked questions

Why does bilirubin rise with fasting?

In Gilbert's syndrome, according to MedlinePlus Genetics, bilirubin mainly rises when the body is under stress, and long periods without food are one of the examples MedlinePlus Genetics gives. The BSG uses this for an isolated raised bilirubin: on a fasting blood sample, total bilirubin should rise further in Gilbert's syndrome.

What causes Gilbert's syndrome?

According to MedlinePlus Genetics, Gilbert's syndrome is caused by changes in the UGT1A1 gene, which holds the instructions for the enzyme that processes bilirubin in the liver cells. According to MedlinePlus Genetics, not everyone with that genetic change develops a raised bilirubin.

Does Gilbert's syndrome often cause jaundice?

No, in Gilbert's syndrome the bilirubin level fluctuates according to MedlinePlus Genetics, and it very rarely rises to a level that causes jaundice.

Bilirubin (Total): sources

  1. den Elzen WPJ, Brouwer N, Thelen MH, Le Cessie S, Haagen I-A, Cobbaert CM. NUMBER: standardized reference intervals in the Netherlands using a 'big data' approach. Clin Chem Lab Med 2018;57(1):42-56. (retrieved 2026) doi.org
  2. Star-shl, Labbepalingen (referentiewaarden per bepaling), star-shl.nl, geraadpleegd 2026-10-01 (retrieved 2026) star-shl.nl
  3. Unilabs, Bepalingenklapper (referentiewaarden per bepaling), bepalingenklapper.nl, geraadpleegd 2026-10-01 (retrieved 2026) bepalingenklapper.nl
  4. Certe, Bepalingenwijzer (referentiewaarden per bepaling), bepalingenwijzer.certe.nl, geraadpleegd 2026-10-01 (retrieved 2026) bepalingenwijzer.certe.nl
  5. Diagnostiek voor U, eLabgids (Referentiewaarden DvU), diagnostiek.getincontrol.eu, geraadpleegd 2026-10-01 (retrieved 2026) diagnostiek.getincontrol.eu
  6. MedlinePlus, Bilirubin Blood Test, U.S. National Library of Medicine, geraadpleegd 2026-10-13 (retrieved 2026) medlineplus.gov
  7. Newsome PN, et al. Guidelines on the management of abnormal liver blood tests. Gut 2018;67(1):6-19. (retrieved 2026) pmc.ncbi.nlm.nih.gov
  8. NVKC, Alles over testen: Bilirubine, allesovertesten.nl, geraadpleegd 2026-10-13 (retrieved 2026) allesovertesten.nl

Test Products

This marker is included in the following test panels.

GLP-1

GLP-1 Baseline Panel

Your starting point before the first injection: blood sugar, cholesterol, pancreas, liver, kidneys, thyroid and nutrients in one measurement.

Insulin (Fasting) ALT (Alanine Aminotransferase) TSH (Thyroid Stimulating Hormone) AST (Aspartate Aminotransferase) HDL Cholesterol HbA1c (Glycated Hemoglobin) Bilirubin (Total) ApoB (Apolipoprotein B) Vitamin B12 Ferritin Potassium Sodium Glucose (Fasting) Total Cholesterol Albumin Lipase Creatinine Vitamin D (25-OH) Triglycerides Bilirubin (Direct) Bilirubin (Indirect) HOMA-IR eGFR (Estimated Glomerular Filtration Rate) LDL Cholesterol Cholesterol/HDL Ratio Non-HDL Cholesterol LDL/HDL Ratio
€214,-

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Bilirubin (Total)

€7,-