Fatty liver test name refers to the diagnostic investigations used to detect and assess hepatic steatosis, commonly known as fatty liver disease. There is no single definitive test; instead, clinicians use a combination of blood tests—particularly liver function tests (LFTs)—and imaging investigations such as abdominal ultrasound and FibroScan. In the UK, diagnosis follows a structured pathway beginning with alanine aminotransferase (ALT) and aspartate aminotransferase (AST) measurements, progressing to non-invasive fibrosis assessment tools like the FIB-4 index and Enhanced Liver Fibrosis (ELF) test. Understanding which tests are appropriate and when to request them is essential for early detection and management of fatty liver disease.

What Tests Are Used to Diagnose Fatty Liver Disease?

Fatty liver disease, medically termed hepatic steatosis, is diagnosed through a combination of clinical assessment, blood tests, and imaging investigations. There is no single definitive test; rather, clinicians use a diagnostic pathway that begins with liver function tests (LFTs) and progresses to more specialised investigations when indicated.

Diagnosis of non-alcoholic fatty liver disease (NAFLD) requires evidence of hepatic steatosis on imaging or histology, alongside exclusion of significant alcohol consumption (above 14 units per week) and other causes of liver disease. It is important to note that NICE guidance does not recommend routine screening or testing for NAFLD in people with type 2 diabetes, metabolic syndrome, or obesity. Assessment is typically prompted by abnormal liver blood tests or incidental imaging findings.

The initial diagnostic approach involves blood tests to assess liver enzyme levels, particularly alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Elevated levels may suggest liver inflammation, though normal results do not exclude fatty liver disease. Additional blood markers help identify metabolic risk factors and exclude alternative diagnoses, including lipid profiles, fasting glucose, and HbA1c.

Imaging investigations play a key role in detecting hepatic steatosis. Abdominal ultrasound scanning remains the first-line imaging modality in UK practice. It is non-invasive, widely available, and can detect moderate to severe hepatic steatosis. More advanced techniques include transient elastography (FibroScan), which measures liver stiffness as a marker of fibrosis, and magnetic resonance imaging (MRI), which provides detailed assessment of fat content and liver architecture.

For people with confirmed NAFLD, non-invasive fibrosis assessment is essential to identify those at risk of advanced liver disease. NICE recommends using the FIB-4 index or NAFLD Fibrosis Score initially, followed by the Enhanced Liver Fibrosis (ELF) test where indicated. In selected cases, liver biopsy may be considered for definitive diagnosis and staging of liver fibrosis, though it is reserved for complex presentations due to its invasive nature.

Blood Tests for Fatty Liver: LFTs and Beyond

Liver function tests (LFTs) are the most commonly requested blood investigations when fatty liver disease is suspected. This panel typically includes ALT, AST, alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT), bilirubin, and albumin. In fatty liver disease, ALT is often elevated more than AST, though both may remain within normal limits in many people with NAFLD. An AST:ALT ratio greater than 1 may suggest more advanced fibrosis or alcohol-related liver disease, though this ratio varies and is not diagnostic. Results should be interpreted using your local laboratory's reference ranges.

Beyond standard LFTs, clinicians request additional blood markers to assess metabolic health and exclude alternative diagnoses. A lipid profile evaluates total cholesterol, LDL, HDL, and triglycerides—abnormalities are common in NAFLD and contribute to cardiovascular risk. Fasting glucose and HbA1c identify diabetes or prediabetes; NAFLD is highly prevalent in people with type 2 diabetes. Full blood count may reveal thrombocytopenia in advanced fibrosis, whilst a coagulation screen assesses synthetic liver function, though normal results do not exclude significant liver disease.

Specialised blood tests help exclude other causes of liver disease. These include hepatitis B and C serology, ferritin and transferrin saturation (for haemochromatosis), autoimmune markers (antinuclear antibodies, anti-smooth muscle antibodies), and alpha-1 antitrypsin levels. Coeliac serology may also be considered given the association between coeliac disease and liver enzyme elevation.

Non-invasive fibrosis scores calculated from blood results are used in UK practice to assess risk of advanced fibrosis in people with confirmed NAFLD. The FIB-4 index combines age, liver enzymes, and platelet count. For adults under 65 years, a FIB-4 below 1.3 suggests low risk of advanced fibrosis, 1.3–2.67 indicates indeterminate risk, and above 2.67 suggests high risk. For adults aged 65 and over, thresholds are adjusted: below 2.0 suggests low risk, 2.0–2.67 indeterminate, and above 2.67 high risk. The NAFLD Fibrosis Score is an alternative tool. These scores help stratify patients for further investigation, such as the Enhanced Liver Fibrosis (ELF) test, which is recommended by NICE for assessing advanced fibrosis. An ELF score of 10.51 or above suggests advanced fibrosis and warrants specialist referral.

Imaging Tests: Ultrasound, FibroScan and MRI

Abdominal ultrasound is the first-line imaging investigation for suspected fatty liver disease in the UK. This non-invasive, radiation-free technique identifies increased echogenicity (brightness) of the liver parenchyma compared to the kidney, indicating fat accumulation. Ultrasound can reliably detect moderate to severe steatosis (affecting more than approximately 30% of hepatocytes) but has limited sensitivity for mild disease and in people with obesity. It also allows assessment of liver size, surface contour, and exclusion of focal lesions or biliary obstruction. Limitations include operator dependence and reduced accuracy in obese patients.

Transient elastography (FibroScan or vibration-controlled transient elastography, VCTE) is used in UK hepatology services to assess liver stiffness, which correlates with fibrosis stage. This non-invasive technique uses ultrasound-based shear wave technology to measure tissue elasticity, expressed in kilopascals (kPa). Approximate thresholds are: below 7 kPa generally indicates minimal fibrosis, whilst readings above 12 kPa suggest advanced fibrosis or cirrhosis. However, these cut-offs vary by device, body mass index, aetiology, and local protocols, and results can be confounded by inflammation, cholestasis, and hepatic congestion. FibroScan also provides a controlled attenuation parameter (CAP) score, which quantifies hepatic steatosis; again, thresholds are approximate and device-dependent. The test takes approximately 10 minutes and is painless, though it may be less reliable in patients with significant obesity or ascites. Results should be interpreted by trained clinicians in the context of clinical findings and local pathways.

Magnetic resonance imaging (MRI) offers the most accurate non-invasive assessment of liver fat content and fibrosis. MRI-proton density fat fraction (MRI-PDFF) precisely quantifies steatosis, whilst magnetic resonance elastography (MRE) measures liver stiffness with greater accuracy than FibroScan. However, MRI is expensive, time-consuming, and not widely available for routine fatty liver assessment in the NHS. It is typically reserved for research settings or when other investigations are inconclusive.

Computed tomography (CT) can incidentally detect fatty liver but is not routinely used for diagnosis due to radiation exposure and lower sensitivity compared to ultrasound and MRI.

When to Request a Fatty Liver Test from Your GP

NICE guidance does not recommend routine screening or testing for NAFLD in people with type 2 diabetes, metabolic syndrome, or obesity. However, you should discuss fatty liver testing with your GP if you have abnormal liver blood tests or if imaging (such as an ultrasound scan performed for another reason) has shown evidence of hepatic steatosis. Assessment is also appropriate if you have symptoms such as unexplained fatigue or right upper quadrant discomfort, or if your GP detects hepatomegaly (enlarged liver) on examination.

If NAFLD is confirmed, your GP will assess your risk of advanced liver fibrosis using non-invasive tests. This typically involves calculating a FIB-4 score or NAFLD Fibrosis Score from routine blood tests. If these scores suggest indeterminate or high risk, your GP may arrange an Enhanced Liver Fibrosis (ELF) test or refer you for a FibroScan, depending on local pathways. An ELF score of 10.51 or above, or a high FIB-4 score, indicates increased risk of advanced fibrosis and warrants specialist hepatology referral.

It is important to discuss alcohol consumption honestly with your GP. The UK Chief Medical Officers' low-risk drinking guideline is 14 units per week for both men and women. Regular intake above this level may suggest alcohol-related liver disease rather than NAFLD, requiring different management approaches. Your GP will also assess for symptoms of advanced liver disease, including jaundice, ascites (abdominal swelling), ankle swelling, easy bruising, or confusion, which necessitate urgent specialist referral.

Individuals taking medications associated with hepatic steatosis (such as corticosteroids, tamoxifen, or methotrexate) or with a family history of liver disease may also benefit from assessment if liver blood tests are abnormal. If you believe a medicine has caused liver-related side effects, you can report suspected adverse reactions via the MHRA Yellow Card scheme at https://yellowcard.mhra.gov.uk.

Understanding Your Fatty Liver Test Results

Interpreting fatty liver test results requires understanding that no single test provides a complete picture. Your GP will consider blood tests, imaging findings, and clinical context together. Many people with NAFLD have normal or only mildly elevated liver enzymes, so normal liver function tests do not exclude fatty liver disease. Conversely, elevated ALT or AST suggests hepatocellular inflammation but does not confirm the diagnosis or indicate severity. Results should be interpreted using your local laboratory's reference ranges.

Ultrasound reports typically describe the liver as showing "increased echogenicity" or "features consistent with hepatic steatosis" when fatty infiltration is present. The report may grade steatosis as mild, moderate, or severe, though this is subjective and semi-quantitative. Importantly, ultrasound cannot reliably distinguish simple steatosis from steatohepatitis (inflammation) or assess fibrosis stage—these require additional investigations.

FibroScan results include two key measurements. The liver stiffness measurement (LSM) in kPa indicates fibrosis risk: approximate thresholds are less than 7 kPa for minimal fibrosis, 7–9 kPa for possible significant fibrosis, 9–12 kPa for advanced fibrosis, and above 12 kPa for probable cirrhosis. The CAP score quantifies steatosis, with higher values indicating greater fat content. These thresholds are approximate and vary by device, body mass index, and aetiology; results should be interpreted by trained clinicians using local protocols and in the context of other findings.

Fibrosis scores calculated from blood tests help risk-stratify patients with confirmed NAFLD. A FIB-4 score below 1.3 (or below 2.0 in adults aged 65 and over) suggests low risk of advanced fibrosis, whilst scores above 2.67 suggest high risk warranting specialist referral. Indeterminate scores (1.3–2.67 in under-65s; 2.0–2.67 in those 65 and over) typically prompt an ELF test. An ELF score of 10.51 or above suggests advanced fibrosis and indicates the need for specialist hepatology input.

Your GP will explain these results in context and discuss whether lifestyle modification alone is appropriate or whether specialist hepatology input is needed. For adults with NAFLD at low risk of advanced fibrosis, NICE recommends re-assessing fibrosis risk approximately every three years, or sooner if risk factors change. Regular monitoring intervals depend on initial findings and fibrosis risk, and your GP will agree a follow-up plan with you.

Frequently Asked Questions