AST (Aspartate Aminotransferase) Blood Test: Normal Ranges, Causes & What Your Results Mean

What Is AST (Aspartate Aminotransferase)?

Aspartate aminotransferase (AST), formerly known as SGOT (serum glutamic-oxaloacetic transaminase), is an enzyme involved in amino acid metabolism. Like ALT, AST catalyses a transamination reaction - specifically, the transfer of an amino group from aspartate to alpha-ketoglutarate, producing oxaloacetate and glutamate. These products feed into the citric acid cycle and gluconeogenesis, making AST an important player in energy metabolism.

Unlike ALT, which is predominantly found in the liver, AST is distributed widely across many tissues. The highest concentrations are found in the heart, liver, skeletal muscle, kidneys, brain, and red blood cells. This broader distribution means that while AST elevation can indicate liver damage, it is less liver-specific than ALT. An elevated AST could originate from the heart (in the case of a myocardial infarction), skeletal muscle (rhabdomyolysis), or the liver.

AST exists in two forms: a cytoplasmic form (cAST) and a mitochondrial form (mAST). In mild liver injury, the cytoplasmic form predominates in blood. In severe liver damage, where the mitochondria themselves are disrupted, the mitochondrial form is released, indicating more extensive cellular destruction. This distinction has implications for the severity of liver disease.

AST is included in standard liver function test (LFT) panels and is most clinically useful when interpreted alongside ALT, ALP, GGT, and bilirubin.

Why Is AST Tested?

AST is tested as part of the investigation and monitoring of several conditions:

• Liver disease screening and monitoring: AST is part of the standard LFT panel. While less liver-specific than ALT, AST is essential for calculating the AST:ALT ratio (De Ritis ratio), which provides valuable diagnostic information.
• Differentiating types of liver disease: The AST:ALT ratio helps distinguish between causes:
  • An AST:ALT ratio greater than 2:1 is strongly suggestive of alcoholic liver disease
  • An AST:ALT ratio less than 1:1 is more typical of non-alcoholic fatty liver disease (NAFLD) and viral hepatitis
  • An AST:ALT ratio greater than 1:1 in chronic liver disease may indicate progression to cirrhosis
• Detecting muscle damage: AST rises in rhabdomyolysis (severe muscle breakdown), polymyositis, and after intense exercise. It is measured alongside creatine kinase (CK) to assess muscle injury.
• Monitoring hepatotoxic medications: Like ALT, AST is monitored during treatment with drugs that can affect the liver.
• Assessing severity of acute liver injury: Very high AST levels (greater than 10 times normal) indicate severe hepatocellular necrosis, as seen in paracetamol overdose, acute viral hepatitis, and ischaemic hepatitis.
• Historical use in cardiac assessment: Before the advent of troponin testing, AST was used to diagnose myocardial infarction. While troponin has replaced it for this purpose, cardiac-origin AST elevation is still occasionally encountered.

Normal AST Ranges

AST is measured in units per litre (U/L). Reference ranges vary slightly between laboratories:

Group	Normal Range (U/L)
Adult men	10–40 U/L
Adult women	10–35 U/L
Children	15–55 U/L (higher in neonates and infants)
Neonates	25–75 U/L

As with ALT, there is a growing argument for lower thresholds - particularly in the context of screening for early liver disease. AST levels even at the upper end of the "normal" range may warrant attention if risk factors are present.

The AST:ALT ratio (De Ritis ratio) is a clinically important derived value:

AST:ALT Ratio	Suggests
Less than 1.0	NAFLD, viral hepatitis, drug-induced liver injury
1.0–2.0	May indicate cirrhosis or mixed aetiology
Greater than 2.0	Strongly suggestive of alcoholic liver disease

What Do High AST Levels Mean?

Elevated AST indicates cell damage in one or more AST-rich tissues. The degree of elevation and the clinical context determine the likely source.

Liver causes

• Alcoholic liver disease: Alcohol causes a characteristic pattern where AST rises more than ALT (AST:ALT ratio greater than 2:1). This is because alcohol depletes hepatic pyridoxal phosphate (vitamin B6), which is required more for ALT production than AST.
• Non-alcoholic fatty liver disease (NAFLD): NAFLD typically causes a greater rise in ALT than AST, but AST may also be elevated. When the AST:ALT ratio shifts above 1 in NAFLD, it may indicate progression to fibrosis or cirrhosis.
• Cirrhosis: As liver disease progresses from fibrosis to cirrhosis, the AST:ALT ratio tends to increase, eventually exceeding 1. This is because damaged liver cells lose proportionally more ALT than AST.
• Acute viral hepatitis: Both AST and ALT can rise to 10–100 times normal, with ALT typically higher than AST.
• Paracetamol overdose: Causes dramatic elevation of both AST and ALT, often exceeding 3,000 U/L. This is a medical emergency.
• Ischaemic hepatitis (shock liver): Sudden loss of blood supply to the liver causes AST and ALT to spike to very high levels, often with an AST:ALT ratio greater than 1.
• Autoimmune hepatitis: An immune-mediated attack on hepatocytes.

Non-liver causes

• Muscle damage (rhabdomyolysis): Crush injuries, extreme exercise, seizures, statins (rarely), and certain drugs can cause skeletal muscle breakdown, releasing AST (and CK) into the bloodstream. If AST is elevated but ALT is normal or only mildly raised, muscle damage should be suspected.
• Myocardial infarction: AST rises 6–8 hours after a heart attack, though troponin is now the primary diagnostic marker.
• Haemolysis: Red blood cells contain AST, so haemolytic anaemias or haemolysed blood samples can cause spurious elevation.
• Strenuous exercise: Intense resistance training, marathon running, and CrossFit-style workouts can cause transient AST (and CK) elevation lasting several days.
• Thyroid disease: Both hypothyroidism and hyperthyroidism can modestly elevate AST.
• Coeliac disease: Unexplained AST elevation is an indication for coeliac screening.

What Do Low AST Levels Mean?

Low AST levels are uncommon and rarely clinically significant. Potential associations include:

• Vitamin B6 deficiency: AST is a B6-dependent enzyme, so severe deficiency can reduce its activity.
• Uraemia: Chronic kidney disease has been associated with reduced transaminase levels.
• Normal variation: Many healthy individuals have AST values at the lower end of the reference range.

A low AST result typically requires no further action.

How to Improve Your AST Levels

Since elevated AST is the clinical concern, the focus is on strategies to reduce raised levels by addressing the underlying cause:

If alcohol-related

• Reduce or stop alcohol consumption: The liver has a remarkable capacity for regeneration. In alcohol-related liver disease, AST levels often begin to normalise within 2–4 weeks of abstinence, provided cirrhosis has not developed.
• Seek support: If you find it difficult to reduce your intake, speak to your GP about alcohol support services, which are available through the NHS.

If related to NAFLD or metabolic syndrome

• Lose weight: A sustained weight loss of 7–10% can resolve steatohepatitis (inflamed fatty liver) and normalise liver enzymes.
• Exercise regularly: Aerobic exercise reduces hepatic fat content independently of weight loss. Aim for 150 minutes of moderate-intensity activity per week.
• Adopt a Mediterranean diet: This dietary pattern, rich in olive oil, oily fish, nuts, vegetables, and whole grains, has been shown to reduce liver fat and transaminase levels in clinical trials.
• Limit sugar and refined carbohydrates: Fructose-sweetened beverages and highly processed foods drive hepatic fat accumulation.

If exercise-related

• Allow adequate recovery: If you exercise intensely, ensure sufficient rest between sessions. AST elevation from exercise is transient and resolves within 3–7 days.
• Inform your doctor: If you are an athlete or regular gym user, mention this before blood tests, as exercise-related AST elevation may be misinterpreted as liver disease. Ideally, avoid intense exercise for 48–72 hours before liver function testing.

General liver support

• Drink coffee: 2–3 cups daily is associated with lower AST, reduced liver fibrosis risk, and protection against liver cancer.
• Maintain adequate vitamin B6: Found in poultry, fish, potatoes, chickpeas, and bananas.
• Stay hydrated and avoid hepatotoxins: Limit paracetamol to recommended doses, avoid recreational drugs, and minimise unnecessary supplements that may stress the liver.

When Should You Get Tested?

Consider having your AST levels checked if you:

• Consume alcohol regularly, particularly if more than 14 units per week
• Are overweight or have been diagnosed with type 2 diabetes
• Experience unexplained fatigue, nausea, or abdominal discomfort
• Have jaundice (yellowing of the skin or eyes)
• Are taking medications that can affect the liver (statins, methotrexate, anti-epileptics)
• Have experienced severe muscle pain or weakness, or have undergone intense physical exertion
• Have a family history of liver disease
• Want a routine health screen, particularly over the age of 40

AST is included in standard liver function panels and is routinely performed as part of comprehensive blood tests.

Which Lola Health Tests Include AST?

AST is a standard component of liver function testing and is included in several Lola Health panels:

• Peak Insights (70 Biomarkers) - Our most detailed panel with full liver function, metabolic, and cardiovascular markers.
• Vital Check (56 Biomarkers) - Broad health screen including full liver enzyme panel.
• Core Health (45 Biomarkers) - Essential health markers including AST and other liver function tests.
• Liver Health Blood Test — Focused panel for thorough liver assessment.

All Lola Health tests use a venous blood draw at one of our nationwide partner clinics. Results are reviewed by a doctor and returned within 4 working days.