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.

Liver Health

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.

This page provides general educational information about fatty liver disease and the blood tests used to investigate it. It is not a substitute for professional medical advice. Always discuss abnormal liver enzymes or metabolic markers with your GP.

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.

Key enzyme: ALT elevated

FIB-4 > 2.67 = specialist referral

Normal LFTs don't exclude fatty liver

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)

Normal: Women: < 35 U/L; Men: < 45 U/L (lab-dependent)

In NAFLD: Mildly to moderately elevated (1-5× upper limit)

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)

Normal: < 35 U/L (both sexes, approximately)

In NAFLD: Often elevated but usually less than ALT

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)

Normal: Women: < 35 U/L; Men: < 50 U/L

In NAFLD: Commonly elevated, often disproportionately so

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

Normal: < 5.5 mmol/L (fasting)

In NAFLD: Often 5.5–7.0 mmol/L (pre-diabetes); may be > 7.0 mmol/L (diabetes)

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)

Normal: < 41 mmol/mol (< 5.9%)

In NAFLD: Often 41–53 mmol/mol (pre-diabetic range) or above

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

Normal: Triglycerides < 1.7 mmol/L; HDL-C > 1.0 (M) / 1.2 (F) mmol/L

In NAFLD: Elevated triglycerides; low HDL; often raised LDL

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)

Normal: 150–400 × 10⁹/L

In NAFLD: Often normal; low platelet count may indicate advanced fibrosis or cirrhosis (portal hypertension)

Required for FIB-4 score calculation. Low platelets in a patient with fatty liver should prompt urgent specialist referral to exclude cirrhosis.

Ferritin

Normal: Males: 30–400 µg/L; Females: 15–200 µg/L

In NAFLD: Often elevated (acute-phase reaction, not iron overload)

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

Low risk

Advanced fibrosis unlikely. Monitor annually with GP, focus on lifestyle modification.

FIB-4 1.3 – 2.67

Indeterminate

Further assessment recommended. FibroScan or hepatology referral. Repeat FIB-4 in 6-12 months.

FIB-4 > 2.67

High risk

Advanced fibrosis or cirrhosis likely. Specialist referral (hepatology/gastroenterology) warranted promptly.

FIB-4 limitations: The score is less accurate in people over 65 (higher false positives) and in those with very low platelet counts from causes unrelated to liver disease. It is a risk stratification tool, not a diagnosis — your doctor will interpret it in the context of your full clinical picture.

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.

The good news: Simple fatty liver (without significant fibrosis) is reversible. Unlike cirrhosis, it does not need to be a life sentence. Consistent lifestyle change — even modest weight loss and regular exercise — can produce dramatic improvements in liver enzymes and liver fat on imaging within 3-6 months.

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 referral

Can be bulk-billed at most collection centres

FBC, glucose, HbA1c, lipids

Fully Medicare-rebatable with GP referral

Standard metabolic workup, no additional cost

Hepatitis B/C serology

Medicare-rebatable

MBS item numbers 69399, 69482

Liver ultrasound

Medicare-rebatable with GP referral

Bulk-billing availability varies by provider

FibroScan

Limited Medicare rebate in some circumstances

Out-of-pocket costs may apply at some centres; referral usually needed

Liver biopsy

Medicare-rebatable as hospital procedure

Reserved for cases where non-invasive tests are inconclusive

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.

The Quick Answer

Why Blood Tests Are Only Part of the Picture

The Key Blood Tests — What Each One Shows

ALT (Alanine Aminotransferase)

AST (Aspartate Aminotransferase)

GGT (Gamma-Glutamyl Transferase)

Fasting Glucose

HbA1c (Glycated Haemoglobin)

Fasting Lipid Profile

Platelet Count (FBC)

Ferritin

The FIB-4 Score — Estimating Fibrosis Risk Without a Biopsy

FIB-4 = (Age × AST) ÷ (Platelet count × √ALT)

FIB-4 < 1.3

FIB-4 1.3 – 2.67

FIB-4 > 2.67

Red Flags — When to Seek Urgent Assessment

ALT or AST > 5× upper limit of normal

FIB-4 score > 2.67

Low platelet count (< 150 × 10⁹/L) with elevated liver enzymes

Jaundice or coagulation abnormalities

Unexplained weight loss with elevated liver enzymes

AST:ALT ratio > 2 in a person with NAFLD

The Australian GP Pathway — From Elevated ALT to Diagnosis

Baseline liver function tests + metabolic screen

Calculate FIB-4 score

Exclude other liver causes

Liver ultrasound

FibroScan or liver biopsy if indicated

Ongoing monitoring

Lifestyle Reversal — What Actually Works

Weight loss

Exercise

Alcohol

Managing metabolic risk factors

Costs and Medicare — What Is Covered in Australia

Liver function tests (LFTs)

FBC, glucose, HbA1c, lipids

Hepatitis B/C serology

Liver ultrasound

FibroScan

Liver biopsy

Related Reading

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