Can Fatty Liver Cause High Bilirubin?

Fatty liver disease and high bilirubin are closely linked, particularly as the condition advances. In early-stage metabolic dysfunction-associated steatotic liver disease (MASLD), bilirubin levels are often normal, but progressive inflammation, fibrosis, or cirrhosis can impair the liver's ability to process and excrete bilirubin, causing levels to rise. Understanding why bilirubin increases, what symptoms to watch for, and when to seek medical advice is essential for anyone managing or at risk of fatty liver disease.

Can fatty liver cause your bilirubin levels to go up?

Yes, fatty liver disease can raise bilirubin, though this is more common in advanced stages involving inflammation, fibrosis, or cirrhosis rather than early disease. Other causes such as Gilbert's syndrome, haemolysis, and gallstones must also be considered.

Fatty liver disease can cause bilirubin levels to rise, although this is more common in advanced stages of the condition rather than in early or mild disease. In the early phase of metabolic dysfunction-associated steatotic liver disease (MASLD, previously called non-alcoholic fatty liver disease), bilirubin is often within the normal range. However, as fat accumulation leads to inflammation (steatohepatitis) and, over time, fibrosis or cirrhosis, the liver's ability to process and excrete bilirubin becomes impaired, and blood levels can increase.

Bilirubin is a yellow pigment produced when red blood cells break down. A healthy liver captures, processes and excretes it into bile. When liver cells are damaged or bile ducts are obstructed, this pathway is disrupted and bilirubin accumulates in the bloodstream. In fatty liver disease, the combination of hepatocyte injury and, in later stages, structural scarring can reduce this processing capacity.

It is worth noting that mildly elevated bilirubin does not always point to fatty liver. Gilbert's syndrome, a common and benign inherited condition, causes intermittent rises in bilirubin without any underlying liver damage.^[1] Other causes include haemolysis (accelerated breakdown of red blood cells), viral hepatitis, drug-induced liver injury, autoimmune liver conditions, and gallstones blocking the bile duct. A raised bilirubin result therefore always needs to be interpreted alongside other liver function tests and clinical context, rather than in isolation.

How does the liver process bilirubin and why does it matter?

The liver processes bilirubin through uptake, conjugation, and excretion into bile; identifying whether unconjugated or conjugated bilirubin is raised helps pinpoint where the pathway is disrupted. Conjugated bilirubin in the blood causes dark urine, while unconjugated does not.

The liver processes bilirubin through a three-stage pathway: uptake from the blood, conjugation within liver cells, and excretion into bile. Understanding this process helps explain why different types of liver disease affect bilirubin in different ways. When red blood cells reach the end of their lifespan, haemoglobin is broken down into haem, which is then converted to unconjugated (indirect) bilirubin. This fat-soluble form travels in the bloodstream bound to albumin and is taken up by hepatocytes (liver cells).

Inside the hepatocyte, enzymes attach glucuronic acid to bilirubin, converting it into conjugated (direct) bilirubin, which is water-soluble.^[2] This conjugated form is then secreted into bile and passes into the small intestine, where gut bacteria convert it into urobilinogen. Most urobilinogen is excreted in faeces, giving stools their characteristic brown colour.

This process matters clinically because the type of bilirubin that is raised helps identify where the problem lies. A rise in unconjugated bilirubin suggests impaired uptake or conjugation, as seen in Gilbert's syndrome or haemolysis. Because unconjugated bilirubin is not water-soluble, it is not excreted by the kidneys and does not darken urine. A rise in conjugated bilirubin, by contrast, points to impaired excretion or bile duct obstruction, as can occur in more advanced fatty liver disease, gallstones, or cholestatic conditions. Conjugated bilirubin is water-soluble and is filtered by the kidneys, which is why urine appears darker in cholestatic or hepatocellular injury. Jaundice, the yellowing of the skin and whites of the eyes, typically becomes visible when total bilirubin rises substantially above the normal range, though the exact threshold can vary between individuals.

What other symptoms suggest your liver is struggling?

Persistent fatigue, right upper abdominal discomfort, jaundice, dark urine, pale stools, itching, and abdominal swelling can all indicate liver dysfunction. Many people with fatty liver disease have no symptoms at all, so routine monitoring is important for those with risk factors.

Fatigue that does not improve with rest is one of the most commonly reported symptoms when the liver is under strain, and it can appear even in early fatty liver disease before bilirubin becomes elevated. Because the liver performs hundreds of metabolic functions, including detoxification, protein synthesis and energy regulation, impaired function can produce a wide range of symptoms that are easy to attribute to other causes.

As fatty liver disease progresses, additional symptoms may develop, including:

• Discomfort or a dull ache in the upper right abdomen, where the liver sits beneath the ribcage

• Nausea or reduced appetite. Note that nausea specifically after fatty meals is more characteristic of biliary problems such as gallstones than of fatty liver disease itself, and should be assessed by a GP

• Unexplained weight loss in more advanced disease

• Jaundice, a yellowing of the skin or whites of the eyes, which indicates significantly elevated bilirubin

• Dark urine or pale, clay-coloured stools, which suggest conjugated bilirubin is not being excreted normally into bile, pointing to cholestatic or hepatocellular injury

• Itching (pruritus), caused by bile salts accumulating in the skin

• Swelling of the abdomen (ascites) or legs, which can occur in cirrhosis. The principal mechanism is portal hypertension causing fluid retention by the kidneys; reduced albumin production by the damaged liver also contributes

If you develop fever alongside right upper abdominal pain and jaundice, seek urgent medical attention, as this combination can indicate cholangitis, an infection of the bile ducts that requires prompt treatment.

It is important to recognise that many people with fatty liver disease, including those with early inflammation, have no symptoms at all. The condition is frequently discovered incidentally during blood tests or an ultrasound scan carried out for another reason. The absence of symptoms does not mean the liver is unaffected, which is why routine monitoring is recommended for people with known risk factors such as obesity, type 2 diabetes, or metabolic syndrome.

Which blood tests does a GP use to check liver and bilirubin health?

A GP requests a liver function test (LFT) panel including bilirubin, ALT, AST, ALP, GGT, and albumin to assess liver health. In fatty liver disease, ALT and GGT often rise before bilirubin becomes abnormal.

A GP will typically request a liver function test (LFT) panel as the first step in assessing both bilirubin levels and overall liver health. This is a group of blood tests measured from a single sample. The standard UK LFT panel includes:

• Total bilirubin (and sometimes split into direct and indirect fractions to identify the cause of any elevation)

• Alanine aminotransferase (ALT) and aspartate aminotransferase (AST), enzymes that leak into the blood when liver cells are damaged

• Alkaline phosphatase (ALP), which is raised in bile duct problems and some bone conditions

• Gamma-glutamyl transferase (GGT), which is sensitive to alcohol use and fatty liver disease

• Albumin, a protein made by the liver whose level falls in chronic liver disease

Prothrombin time (PT) or INR is a clotting measure that reflects the liver's synthetic function, but in UK practice this is a separate test requested when there is concern about liver synthetic function, rather than part of the routine LFT panel.

In the context of fatty liver disease, ALT and GGT are often the first markers to rise, sometimes before bilirubin becomes abnormal. A GP may also request a full blood count, fasting glucose and HbA1c, lipid profile, and renal function tests to assess the broader metabolic picture.

Where the cause of abnormal LFTs is not immediately clear, UK practice (as outlined in BSG guidance on abnormal liver blood tests) includes first-line aetiology testing: hepatitis B surface antigen, hepatitis C antibody, autoimmune markers (antinuclear antibody, anti-smooth muscle antibody, anti-mitochondrial antibody), ferritin and transferrin saturation, and in some cases a coeliac screen.^[7]

If initial blood tests suggest significant liver disease, further investigations may include a liver ultrasound scan, which can detect fat deposition. For assessing the degree of fibrosis in adults with confirmed NAFLD or MASLD, NICE guidance (NG49 and DG34) supports use of the NAFLD Fibrosis Score (NFS) as a first-line tool, with the Enhanced Liver Fibrosis (ELF) test to assess for advanced fibrosis. The FIB-4 index is also used in UK hepatology and primary care pathways, as described in BSG guidance, though it is not the primary tool specified by NICE.^[7][10] In some cases, a liver biopsy or specialist referral may be needed to confirm the degree of fibrosis.

When should you see a doctor about raised bilirubin or fatty liver?

See a GP promptly if you notice jaundice, dark urine, pale stools, unexplained itching, or abdominal swelling. Fever with right upper abdominal pain and jaundice requires urgent assessment via NHS 111 or A&E.

You should contact your GP promptly if you notice yellowing of your skin or the whites of your eyes, as jaundice always warrants clinical assessment to identify the underlying cause. Other symptoms that should prompt a GP appointment include persistent dark urine, pale stools, significant abdominal swelling, or unexplained itching that does not settle. These can indicate that bile flow is obstructed or that liver function is significantly impaired.

If you develop fever alongside right upper abdominal pain and jaundice (known as Charcot's triad), seek urgent medical attention or call NHS 111, as this combination can indicate cholangitis, which requires prompt assessment and treatment. For severe symptoms such as sudden, severe abdominal pain or collapse, call 999 or go to A&E.

If you have already been told you have fatty liver disease and you develop any of the above symptoms, or if you experience sudden worsening of fatigue, confusion, or abdominal pain, contact your GP or call NHS 111 for advice. Confusion or marked drowsiness alongside known liver disease can be a sign of hepatic encephalopathy, which requires urgent assessment.

For people who have risk factors for fatty liver disease, such as obesity, type 2 diabetes, high blood pressure, or raised cholesterol, it is worth discussing liver health proactively with a GP even in the absence of symptoms. NICE guidance (NG49) sets out pathways for assessing fibrosis in adults with confirmed NAFLD or MASLD, including use of the NAFLD Fibrosis Score and the ELF test. BSG and UK hepatology pathways also support fibrosis assessment in people with type 2 diabetes who have evidence of fatty liver disease, though this is not a universal NICE mandate for all people with type 2 diabetes.^[7][8] Early identification allows lifestyle interventions, including weight loss and dietary changes, to be started before significant liver damage occurs.

When seeking an online consultation about metabolic health or weight management, Bolt Pharmacy is a GPhC-registered UK online pharmacy offering prescriber-led consultations, with pharmacist support throughout. Addressing underlying metabolic risk factors, including excess weight, is central to managing fatty liver disease and reducing the risk of progression.

Scientific References

1. Gilbert's syndrome.
2. The molecular mechanism of hepatocyte bilirubin transport.
3. Cholestasis – Treatment summaries.
4. Non-alcoholic fatty liver disease (NAFLD).
5. Liver disease.
6. Rezdiffra – Public Assessment Report.
7. Guidelines on the management of abnormal liver blood tests.
8. Metabolic dysfunction-associated steatotic liver disease (MASLD) – NG49.
9. Metabolic dysfunction-associated steatotic liver disease – NG49 recommendations for research.
10. Non-alcoholic fatty liver disease – Protocol [HTG655].
11. LIVERFASt for assessing and monitoring liver fibrosis.

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