Blood Tests for Fatty Liver (NAFLD/MAFLD)
What ALT, AST, GGT, and the FIB-4 score mean — and the pathway from abnormal liver enzymes to diagnosis and treatment.
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The Quick Answer
Fatty liver disease (now often called MAFLD — metabolic dysfunction-associated fatty liver disease, or the older term NAFLD) is a buildup of fat in liver cells not caused by excessive alcohol. It affects an estimated 1 in 3 Australian adults, making it the most common liver condition in the country.
The spectrum runs from simple steatosis (fat accumulation, largely harmless) to NASH(non-alcoholic steatohepatitis — fat plus inflammation plus liver cell damage) to fibrosis and cirrhosis. The key blood test goal is to identify which patients are on the progressive end of this spectrum.
Why Blood Tests Are Only Part of the Picture
Fatty liver disease is often silent. Most people with NAFLD have no symptoms at all. Liver enzymes may be normal even when a significant amount of liver fat is present. This is why fatty liver is often found incidentally on an ultrasound ordered for another reason (abdominal pain, gallstones), or when a GP notices elevated ALT or GGT in routine blood work.
The key question blood tests help answer is not just whether fatty liver is present, but whether it has progressed to NASH or fibrosis — which is where serious long-term risk lies. The FIB-4 score, derived entirely from routine blood test values, provides a validated way to estimate this risk without the need for liver biopsy in most cases.
Blood tests also identify the metabolic drivers that need to be addressed: insulin resistance, dyslipidaemia, and obesity-related hypertriglyceridaemia. Treating the metabolic root cause is the most effective way to reverse fatty liver disease.
The Key Blood Tests — What Each One Shows
A comprehensive NAFLD/MAFLD workup includes liver enzymes, a metabolic screen, and tests to exclude other liver conditions that can mimic fatty liver disease.
ALT (Alanine Aminotransferase)
The primary hepatocellular injury marker. In NAFLD/MAFLD, ALT elevation reflects hepatocyte inflammation (NASH). Note: ALT can be normal even with significant steatosis.
AST (Aspartate Aminotransferase)
AST:ALT ratio is diagnostically useful. In NAFLD, ALT > AST (ratio < 1). In alcoholic hepatitis or cirrhosis, AST > ALT (ratio > 2). A rising ratio in NAFLD can signal progression to advanced fibrosis.
GGT (Gamma-Glutamyl Transferase)
Very sensitive to alcohol and liver fat. A GGT persistently elevated despite alcohol abstinence strongly supports fatty liver disease. Also elevated by medications, biliary disease.
Fasting Glucose
Insulin resistance is the key driver of NAFLD. Impaired fasting glucose and type 2 diabetes are both strongly associated with fatty liver and progression to NASH.
HbA1c (Glycated Haemoglobin)
Reflects average blood glucose over 3 months. Identifies pre-diabetes and diabetes driving metabolic liver disease. An HbA1c ≥ 48 mmol/mol (≥ 6.5%) on two tests confirms diabetes.
Fasting Lipid Profile
Dyslipidaemia (especially elevated triglycerides and low HDL) is tightly linked to NAFLD through shared metabolic pathways. The fasting lipid panel is essential in every NAFLD workup.
Platelet Count (FBC)
Required for FIB-4 score calculation. Low platelets in a patient with fatty liver should prompt urgent specialist referral to exclude cirrhosis.
Ferritin
High ferritin in NAFLD usually reflects inflammation, not iron overload. However, iron overload can worsen NAFLD. If ferritin is very high (> 1000 µg/L), check transferrin saturation to exclude haemochromatosis.
The FIB-4 Score — Estimating Fibrosis Risk Without a Biopsy
The FIB-4 score is endorsed by Australian liver disease guidelines as the recommended first-line non-invasive fibrosis assessment tool. It uses four values that are available from a standard blood test:
FIB-4 = (Age × AST) ÷ (Platelet count × √ALT)
FIB-4 < 1.3
Advanced fibrosis unlikely. Monitor annually with GP, focus on lifestyle modification.
FIB-4 1.3 – 2.67
Further assessment recommended. FibroScan or hepatology referral. Repeat FIB-4 in 6-12 months.
FIB-4 > 2.67
Advanced fibrosis or cirrhosis likely. Specialist referral (hepatology/gastroenterology) warranted promptly.
Red Flags — When to Seek Urgent Assessment
ALT or AST > 5× upper limit of normal
Significant hepatitis requiring urgent investigation. Causes include medication toxicity, viral hepatitis, autoimmune hepatitis, or advanced alcoholic hepatitis. Do not attribute to simple NAFLD without excluding these.
FIB-4 score > 2.67
High probability of advanced fibrosis. Australian liver disease guidelines recommend specialist referral (hepatology/gastroenterology) and further non-invasive fibrosis assessment (FibroScan or liver biopsy).
Low platelet count (< 150 × 10⁹/L) with elevated liver enzymes
Thrombocytopenia in the context of liver disease suggests portal hypertension secondary to cirrhosis. Urgent assessment needed.
Jaundice or coagulation abnormalities
Yellow skin or eyes, or a prolonged INR/PT, indicate severely impaired liver synthetic function. This is an emergency — present to an ED or call your GP immediately.
Unexplained weight loss with elevated liver enzymes
Always exclude hepatocellular carcinoma (HCC), which can develop in cirrhotic livers. AFP (alpha-fetoprotein) and ultrasound surveillance are recommended 6-monthly in patients with cirrhosis.
AST:ALT ratio > 2 in a person with NAFLD
This ratio pattern is unusual for simple NAFLD and suggests either significant alcohol use, cirrhosis, or an alternative diagnosis. Prompt specialist review is warranted.
The Australian GP Pathway — From Elevated ALT to Diagnosis
Baseline liver function tests + metabolic screen
ALT, AST, GGT, ALP (alkaline phosphatase), bilirubin, albumin, fasting glucose, HbA1c, fasting lipids (including triglycerides). FBC for platelets. This gives a comprehensive picture of both liver injury and metabolic drivers.
Calculate FIB-4 score
FIB-4 = (Age × AST) ÷ (Platelet count × √ALT). Results: < 1.3 = low fibrosis risk; 1.3–2.67 = indeterminate; > 2.67 = high fibrosis risk. Your GP or pathology report software may calculate this automatically.
Exclude other liver causes
Hepatitis B surface antigen (HBsAg), hepatitis C antibody (HCV Ab), ANA and anti-smooth muscle antibody (autoimmune hepatitis screen), iron studies (ferritin, transferrin saturation), caeruloplasmin if under 40 (Wilson's disease). These are rarely positive but important to exclude.
Liver ultrasound
Ultrasound detects moderate-to-severe steatosis (sensitivity ~80% for > 30% fat infiltration). It also screens for liver masses and gallstones. A "bright" or "echogenic" liver on ultrasound report is consistent with fatty change.
FibroScan or liver biopsy if indicated
FibroScan (transient elastography) measures liver stiffness as a surrogate for fibrosis — increasingly available in Australia at specialist centres and some GP practices. It is non-invasive, painless, and takes under 10 minutes. Liver biopsy remains the gold standard for staging but is reserved for ambiguous or high-risk cases.
Ongoing monitoring
For confirmed NAFLD with low FIB-4 and normal ultrasound: annual liver enzymes, FIB-4, and metabolic screen. If FIB-4 is in the indeterminate range: FibroScan every 1-2 years and six-monthly review with GP. Specialist follow-up for confirmed advanced fibrosis or cirrhosis.
Lifestyle Reversal — What Actually Works
Weight loss
A weight loss of 7-10% of body weight is the most evidence-based intervention for reversing NAFLD. Studies consistently show this reduces liver fat on imaging, normalises liver enzymes, and can reverse early fibrosis. Even 3-5% weight loss reduces liver fat and improves metabolic markers. Any sustainable dietary approach that achieves a caloric deficit is acceptable — there is no single “best diet” for NAFLD.
Exercise
Regular aerobic exercise (150-300 minutes per week of moderate-intensity activity, or 75-150 minutes of vigorous activity) reduces liver fat independently of weight loss. Resistance training also benefits liver fat and metabolic markers. Reducing sitting time and increasing incidental activity has additional metabolic benefits.
Alcohol
Even moderate alcohol use worsens NAFLD progression. Australian liver disease guidelines recommend minimising alcohol consumption in all patients with fatty liver disease, even those classified as “NAFLD” rather than alcoholic liver disease. Many specialists advise complete abstinence in patients with NASH or advanced fibrosis.
Managing metabolic risk factors
Treating type 2 diabetes (GLP-1 receptor agonists like semaglutide and pioglitazone show benefit in NASH trials), dyslipidaemia, and hypertension are all important parts of comprehensive NAFLD management. Some medications used for other metabolic conditions may also benefit the liver — discuss with your specialist.
Costs and Medicare — What Is Covered in Australia
Standard liver function tests (ALT, AST, GGT, ALP, bilirubin, albumin) and the metabolic screen (glucose, HbA1c, lipids, FBC) are all covered by Medicare when ordered by a GP. The FIB-4 score is calculated from these existing tests at no extra cost.
Liver function tests (LFTs)
Fully Medicare-rebatable with GP referralCan be bulk-billed at most collection centres
FBC, glucose, HbA1c, lipids
Fully Medicare-rebatable with GP referralStandard metabolic workup, no additional cost
Hepatitis B/C serology
Medicare-rebatableMBS item numbers 69399, 69482
Liver ultrasound
Medicare-rebatable with GP referralBulk-billing availability varies by provider
FibroScan
Limited Medicare rebate in some circumstancesOut-of-pocket costs may apply at some centres; referral usually needed
Liver biopsy
Medicare-rebatable as hospital procedureReserved for cases where non-invasive tests are inconclusive
Blood Tests for Fatty Liver (NAFLD/MAFLD) — Frequently Asked Questions
What blood tests show fatty liver?
The main blood tests used to detect and monitor fatty liver are ALT (alanine aminotransferase), AST (aspartate aminotransferase), and GGT (gamma-glutamyl transferase). A raised ALT with a normal AST, in the absence of heavy alcohol use, is the most common pattern in NAFLD. The FIB-4 score — calculated from age, AST, ALT, and platelet count — is a useful non-invasive way to estimate fibrosis risk. Fasting glucose, HbA1c, and a fasting lipid profile are also essential because metabolic risk factors drive fatty liver disease.
Can you have fatty liver with normal liver blood tests?
Yes. Liver blood tests (ALT, AST, GGT) are often completely normal in people with simple fatty liver (hepatic steatosis), even when a significant proportion of the liver is infiltrated with fat. This is why ultrasound is commonly used to diagnose fatty liver when metabolic risk factors are present, even if liver enzymes are within range. Normal LFTs do not exclude fatty liver.
What is a normal ALT level in Australia?
Most Australian labs report the upper limit of normal for ALT as 35-45 U/L in women and 45-55 U/L in men. Some international guidelines suggest that the true upper limit of normal in metabolically healthy individuals is lower — around 25 U/L for women and 35 U/L for men. An ALT persistently above the upper limit of normal for your lab, without an obvious cause like medication, should be investigated.
What is the FIB-4 score and what does it mean?
The FIB-4 score estimates the risk of advanced liver fibrosis using a simple formula: Age × AST ÷ (Platelet count × √ALT). A score below 1.3 suggests low fibrosis risk, between 1.3 and 2.67 is indeterminate (requires further testing), and above 2.67 suggests high fibrosis risk warranting specialist referral. The FIB-4 is endorsed by Australian liver disease guidelines as the preferred initial non-invasive fibrosis assessment.
Can fatty liver be reversed?
Simple fatty liver (without significant fibrosis) is often reversible with lifestyle change. Weight loss of 7-10% of body weight consistently reduces liver fat on imaging and normalises liver enzymes in the majority of patients. Even without reaching a healthy BMI, modest weight loss of 3-5% can reduce liver fat. Regular aerobic exercise reduces liver fat independently of weight loss. There are no approved medications specifically for NAFLD/MAFLD in Australia, though several are in late-stage trials.
Does a high GGT always mean alcohol or fatty liver?
Not always. GGT is a sensitive but non-specific liver enzyme. It is elevated by alcohol use (even modest amounts), fatty liver disease, certain medications (anticonvulsants, statins), biliary disease (gallstones, cholestasis), and thyroid disease. In isolation, a mildly elevated GGT is not diagnostic of any single condition. Its most useful role is in combination with other liver enzymes and the clinical history.
Should I have an ultrasound if my ALT is mildly elevated?
In Australia, a persistently elevated ALT (2-3 measurements over 3-6 months) is generally an indication for liver ultrasound. It can detect moderate-to-severe fatty infiltration (sensitivity decreases for mild steatosis), identify structural abnormalities, and screen for focal lesions. An ultrasound that shows fatty changes does not tell you the degree of inflammation or fibrosis — that requires additional assessment such as FibroScan (transient elastography) or FIB-4 score.
Related Reading
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This page provides general educational information about fatty liver disease (NAFLD/MAFLD) and the blood tests used to assess it. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your GP about abnormal liver enzyme results. SmarterBlood does not provide medical care.