Liver Function Tests (LFTs): What Your Results Mean
Your liver performs over 500 vital functions every day. Liver function tests measure enzymes and proteins that reveal how well this essential organ is working.
Your Liver: The Body’s Chemical Factory
Weighing around 1.5 kg, the liver is your largest internal organ and the only one that can regenerate itself. It processes virtually everything you eat, drink, breathe, or absorb through your skin. Here are its six major roles:
Detoxification
Filters blood, breaks down toxins, alcohol, and medications into harmless byproducts
Metabolism
Processes nutrients from food, stores glycogen for energy, regulates blood sugar
Production
Makes bile for fat digestion, produces essential proteins and cholesterol
Storage
Stores vitamins A, D, E, K, B12, iron, and copper for when the body needs them
Immune Function
Kupffer cells in the liver destroy bacteria and old red blood cells from the bloodstream
Blood Clotting
Produces clotting factors (I, II, V, VII, IX, X, XI) and the anticoagulant proteins C and S
The 7 Key Liver Markers
Each liver marker measures a different aspect of liver health. Understanding what each one tells you helps you and your doctor interpret your results as a complete picture, not isolated numbers.
ALT
Alanine Aminotransferase
Liver cell damage. ALT is found predominantly in the liver, making it the most specific marker for hepatocyte injury.
Elevated in
Non-alcoholic fatty liver disease (NAFLD)
Viral hepatitis (A, B, C)
Drug-induced liver injury (paracetamol, statins)
Autoimmune hepatitis
Celiac disease
Low in
Vitamin B6 deficiency (ALT requires B6 as a cofactor)
Advanced cirrhosis (few functioning hepatocytes remain)
AST
Aspartate Aminotransferase
Cell damage in liver, heart, muscle, and kidneys. Less specific to the liver than ALT because it is present in multiple organs.
Elevated in
Alcoholic liver disease (AST typically > ALT)
Cirrhosis
Heart attack (myocardial infarction)
Muscle injury or rhabdomyolysis
Hemolysis (red blood cell breakdown)
Low in
Vitamin B6 deficiency
Uremia (chronic kidney disease)
ALP
Alkaline Phosphatase
Bile duct obstruction and bone metabolism. ALP is found in the liver (bile ducts), bones, kidneys, and intestines.
Elevated in
Bile duct obstruction (gallstones, tumours)
Primary biliary cholangitis
Bone diseases (Paget's disease, fractures)
Pregnancy (placental ALP, normal in third trimester)
Growing children (bone growth, not pathological)
Low in
Hypothyroidism
Zinc or magnesium deficiency
Pernicious anaemia
GGT
Gamma-Glutamyl Transferase
Bile duct damage and enzyme induction. GGT is highly sensitive to alcohol consumption and certain medications.
Elevated in
Alcohol consumption (even moderate amounts)
Bile duct obstruction
Enzyme-inducing drugs (phenytoin, carbamazepine, rifampicin)
Fatty liver disease
Pancreatic disease
Low in
Hypothyroidism
GGT is rarely clinically low
Bilirubin
Total Bilirubin (includes Direct and Indirect)
Bilirubin is a yellow pigment produced from the breakdown of haemoglobin in red blood cells. The liver conjugates (processes) bilirubin for excretion in bile.
Elevated in
Jaundice (visible when bilirubin exceeds ~35 µmol/L)
Haemolytic anaemia (increased red cell destruction)
Gilbert's syndrome (benign, affects ~5% of population)
Hepatitis or cirrhosis
Bile duct obstruction
Low in
Low bilirubin is not typically clinically significant
May be seen with certain medications
Albumin
Albumin (Serum)
The liver's protein-production capacity. Albumin is the most abundant protein in blood plasma and is made exclusively by the liver. It maintains oncotic pressure and transports hormones, drugs, and fatty acids.
Elevated in
Dehydration (relative increase due to haemoconcentration)
High albumin is rarely a clinical concern
Low in
Chronic liver disease or cirrhosis (reduced production)
Nephrotic syndrome (protein lost in urine)
Malnutrition or malabsorption
Chronic inflammation (albumin is a negative acute-phase reactant)
Burns or major surgery
Total Protein
Total Protein (Albumin + Globulins)
The combined concentration of albumin and globulins in the blood. The albumin-to-globulin (A/G) ratio provides additional diagnostic information.
Elevated in
Chronic infections (increased globulin production)
Multiple myeloma (monoclonal gammopathy)
Autoimmune diseases (polyclonal gammopathy)
Dehydration
Low in
Liver disease (reduced albumin production)
Kidney disease (protein lost in urine)
Malabsorption syndromes
Immunodeficiency (reduced globulin production)
Common Patterns & What They Mean
Doctors rarely interpret a single liver enzyme in isolation. Instead, they look at the overall pattern across multiple markers to narrow down the likely cause. The table below shows the five most common diagnostic patterns.
| Pattern | ALT | AST | ALP | GGT | Bilirubin | Suggests |
|---|---|---|---|---|---|---|
| Hepatocellular damage | High | High | Normal/Mild | Normal/Mild | Normal/High | Viral hepatitis, drug injury, fatty liver, autoimmune hepatitis |
| Cholestatic pattern | Normal/Mild | Normal/Mild | High | High | Normal/High | Gallstones, bile duct obstruction, primary biliary cholangitis |
| Alcohol-related | Moderate | High (AST>ALT) | Normal/Mild | Very High | Normal/High | Alcoholic hepatitis, alcoholic fatty liver disease |
| Drug-induced | High | High | Mild/High | High | Variable | Medications (statins, antibiotics, paracetamol, NSAIDs) |
| Chronic liver disease | Normal/Mild | Normal/Mild | Normal/Mild | Variable | High | Cirrhosis (often with low albumin and prolonged clotting time) |
The AST:ALT Ratio
One of the most useful diagnostic tools in liver medicine is the ratio of AST to ALT. While neither enzyme alone tells the full story, their relative levels can point toward a specific diagnosis.
Ratio < 1
ALT is higher than AST
Suggests viral hepatitis or non-alcoholic fatty liver disease (NAFLD). This is the most common pattern seen in routine blood tests and often responds well to lifestyle changes.
Ratio 1–2
AST slightly exceeds ALT
Could indicate various liver conditions. This is a non-specific range seen in early cirrhosis, advanced fibrosis, or mixed-cause liver disease. Further investigation is usually needed.
Ratio > 2
AST is much higher than ALT
Strongly suggests alcoholic liver disease. The classic 2:1 ratio occurs because alcohol depletes hepatic B6 (reducing ALT more than AST) and causes mitochondrial damage (releasing more AST).
Common Causes of Elevated Liver Enzymes
The degree of elevation often matters more than which enzyme is elevated. Doctors classify elevations by how many times above the upper limit of normal (ULN) the result falls.
Most common, often incidental finding
Non-alcoholic fatty liver disease (NAFLD) -- the most common cause worldwide
Medications (statins, NSAIDs, antibiotics, herbal supplements)
Celiac disease (consider screening when ALT is mildly elevated without explanation)
Thyroid disorders (both hyper- and hypothyroidism)
Strenuous exercise (AST and ALT can rise transiently after intense workouts)
Warrants investigation
Chronic hepatitis B or C
Autoimmune hepatitis
Alcoholic liver disease
Haemochromatosis (iron overload)
Alpha-1 antitrypsin deficiency
Wilson's disease (copper overload, especially in younger patients)
Urgent medical attention required
Acute viral hepatitis (A, B, or E)
Drug-induced liver injury (particularly paracetamol/acetaminophen overdose)
Ischaemic hepatitis (shock liver, from reduced blood flow)
Autoimmune hepatitis flare
Budd-Chiari syndrome (hepatic vein thrombosis)
Toxin exposure (Amanita mushroom poisoning, industrial solvents)
Lifestyle & Your Liver
The liver has a remarkable capacity for repair. Many causes of mildly elevated liver enzymes are reversible with lifestyle modifications. Here are the evidence-based strategies:
Alcohol
Guidelines recommend no more than 10 standard drinks per week, with at least 2 alcohol-free days. Heavy drinking (more than 4 drinks in a session) is particularly damaging. GGT typically normalises within 2-6 weeks of abstinence.
Medications
Paracetamol (acetaminophen) is the leading cause of acute liver failure in developed countries. Never exceed 4 g/day (2 g/day if you drink regularly). Inform your doctor about all supplements, including herbal products, as many are hepatotoxic.
Coffee
Multiple large studies show that 2-3 cups of coffee per day is associated with lower risk of liver fibrosis, cirrhosis, and hepatocellular carcinoma. The benefit appears to come from coffee itself, not just caffeine, and applies to both filtered and espresso preparations.
Exercise
Regular physical activity reduces liver fat even without weight loss. Aim for at least 150 minutes of moderate-intensity exercise per week. Both aerobic exercise and resistance training have proven benefits for liver health.
Weight Management
NAFLD affects approximately 25% of the global population. Losing 5-10% of body weight can significantly reduce liver fat and inflammation. Even modest weight reduction of 3-5% can improve steatosis (fatty change), while 7-10% loss can resolve steatohepatitis.
Hepatitis Vaccination
Hepatitis A and B vaccines are safe, effective, and widely available. Hepatitis B vaccination is especially important as chronic infection can lead to cirrhosis and liver cancer. Check with your doctor if your immunity needs boosting.
Track Your Liver Markers Over Time
Upload your blood test results to SmarterBlood and watch your ALT, AST, GGT, and other liver markers trend over time. See whether lifestyle changes are making a difference with clear, easy-to-read graphs.