Fatty liver disease is assessed with a clinician’s review of health history and risk factors, blood tests, and imaging. For many people, evaluation starts with the FIB-4 score, which estimates the risk of advanced liver scarring; an elevated or uncertain result may lead to a second test such as FibroScan or the ELF blood test. These tests help guide care, but they do not all measure the same thing, and they cannot reveal every microscopic change in the liver.
What diagnosis means today: MASLD, fat, and liver scarring
Many people still use “fatty liver” or see the older term NAFLD in their records. Current terminology includes metabolic dysfunction-associated steatotic liver disease (MASLD), which describes steatotic liver disease accompanied by at least one cardiometabolic risk factor and without harmful alcohol intake. The terms are not interchangeable in every clinical circumstance, so a clinician considers alcohol exposure and other possible causes rather than relying on a label alone. The 2024 EASL-EASD-EASO guideline sets out the updated terminology.
Tests address different questions. Steatosis means excess fat in the liver; fibrosis is scar tissue; and steatohepatitis involves liver-cell injury and inflammation. Seeing fat does not establish whether scarring is present, and a risk score for fibrosis is not itself a diagnosis of fatty liver.
Why a clinician may investigate
Evaluation can begin after fat is noticed on an imaging scan, after persistently abnormal liver blood tests, or because a person has metabolic risks such as diabetes or excess weight. A clinician reviews alcohol use, medicines and supplements, metabolic and cardiovascular history, and other possible causes of liver fat or liver injury. An ultrasound finding of fat does not show whether advanced fibrosis is present. AASLD guidance recommends risk assessment when MASLD is suspected, using non-invasive tests to help identify people who may have advanced fibrosis.
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Routine blood tests can contribute to the assessment, but liver enzymes such as AST and ALT cannot by themselves establish the amount of fat or stage fibrosis. A common first-step tool is FIB-4, calculated from age, AST, ALT, and platelet count. It estimates the likelihood of advanced fibrosis; it does not prove or rule out all stages of liver disease.
In the AASLD pathway, a FIB-4 below 1.3 generally supports follow-up in primary care for many adults, while a result at or above 1.3 prompts consideration of secondary assessment. For people older than 65, AASLD uses a threshold above 2.0 for that next step. FIB-4 is less accurate below age 35 and should not be used during acute illness. These are pathway-specific thresholds, not universal diagnostic cutoffs. AASLD’s clinical resource and its 2023 practice guidance describe the approach.
What happens after FIB-4?
If FIB-4 is elevated, results are unclear, or clinical concern remains high, a clinician may order another non-invasive test or seek specialist input. The tests below answer related but different questions; they are not interchangeable.
| Test | What it measures | How it is used |
|---|---|---|
| Ultrasound | Can show liver fat; does not establish whether advanced fibrosis is present. | May reveal steatosis incidentally, but does not replace fibrosis risk assessment. |
| VCTE (transient elastography, often called FibroScan) | Measures liver stiffness as an indicator of fibrosis risk. Its controlled attenuation parameter can estimate steatosis. | Often used as a second-stage assessment after FIB-4 or when suspicion remains. |
| ELF blood test | Measures blood markers related to fibrosis. | Can provide a secondary fibrosis-risk assessment; it does not directly image the liver. |
| MRI-based testing | Can provide additional information about liver fat or fibrosis, depending on the technique. | A clinician may consider it when non-invasive results are indeterminate or do not agree. |
The European guideline supports a multi-step approach: start with a blood-based score such as FIB-4, then use elastography when fibrosis remains suspected or a person is in a high-risk group; ELF may be an alternative. The choice depends on the clinical question, age, other health factors, and test availability. EASL-EASD-EASO’s 2024 guideline describes this approach.
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Thresholds also vary by pathway. For example, the AGA’s 2026 clinical care pathway describes FIB-4 below 1.3 (or below 2.0 at age 65 or older), VCTE stiffness below 8 kPa, and ELF below 9.2 as results that generally indicate low risk within that pathway. These figures should be interpreted in their pathway and clinical context, not as universal cutoffs. AGA’s clinical care pathway also provides examples of higher thresholds that may warrant further evaluation.
When is a liver biopsy needed?
Most people with MASLD do not need a biopsy for routine management. A clinician may consider one when a definite diagnosis of steatohepatitis is needed, another possible liver condition must be assessed, non-invasive results leave important uncertainty, or clinical suspicion remains high. Biopsy can show microscopic features such as ballooning and lobular inflammation that non-invasive tests cannot fully assess. The 2024 EASL-EASD-EASO guideline explains its role and limitations.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How often should fatty liver be monitored?
There is no single schedule for everyone. In the AASLD pathway, reassessment is described every 1–2 years for people with prediabetes or type 2 diabetes, or with multiple metabolic risk factors, and every 2–3 years for lower-risk people without prediabetes or type 2 diabetes and with fewer metabolic risks. Age affects how FIB-4 is interpreted; elevated scores may call for secondary testing or specialist review rather than simply waiting for the next routine check. AASLD’s clinical resource sets out these intervals. Other pathways may use different thresholds and follow-up timing, so the clinician should apply one pathway consistently rather than combine cutoffs from different organizations.
Follow-up should also address health conditions associated with MASLD, not just liver test results. The European guideline recommends checking relevant comorbidities at diagnosis and during regular follow-up, including:
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- Type 2 diabetes and blood sugar risk
- Blood lipids and blood pressure
- Kidney disease
- Sleep apnoea
- Cardiovascular risk
The EASL-EASD-EASO guideline includes these conditions in MASLD follow-up.
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