ALT blood test: what the result means

Alanine aminotransferase (ALT, also called ALAT or GPT) takes part in the metabolism of amino acids and builds up mostly in the liver. In a healthy body there is little of it in the blood. When liver cells are damaged — by fat building up, viral hepatitis, alcohol, medicines or impaired blood flow — the enzyme is released into the blood and its level rises. ALT is more specific to the liver than AST, which is also found in muscle and in the heart, so the two are assessed together: the ratio of ALT to AST helps suggest the cause. A liver test panel usually consists of ALT, AST, GGT, alkaline phosphatase and bilirubin. A small rise in ALT is often without symptoms and is found by chance — the most common cause in Lithuania, as across Europe, is fatty liver disease linked to being overweight.

• As a preventive check, as part of a liver test panel — especially when there is overweight or diabetes, or when alcohol is used
• When there are signs of liver disease: tiredness, nausea, pain on the right side below the ribs, yellowed skin or eyes, dark urine
• When taking medicines that can damage the liver — for monitoring
• When ill with hepatitis or after having had it — to follow how it develops
• When keeping an eye on fatty liver disease

A raised ALT indicates damage to liver cells. The most common causes are fatty liver disease, viral hepatitis, alcohol and medicines that affect the liver (including paracetamol in large doses). Rarer ones are haemochromatosis, cirrhosis, impaired blood supply to the liver, mononucleosis, inflammation of the pancreas and tumours. How much it is raised and how it changes over time matter more than a one-off value.

• Fatty liver disease — the most common cause when there is overweight
• Viral hepatitis
• Alcohol
• Medicines that affect the liver, including paracetamol in large doses
• Haemochromatosis — a build-up of iron
• Cirrhosis
• Impaired blood supply to the liver (ischaemia)
• Mononucleosis
• Inflammation of the pancreas
• Liver tumours

Symptoms that may go with a raised ALT

• Often there are no symptoms — it is found by chance
• Tiredness, nausea
• Pain or heaviness on the right side below the ribs
• Yellowed skin or whites of the eyes, dark urine

• AST, GGT, alkaline phosphatase, bilirubin — together they show the nature of the damage
• Alcohol, medicines and supplements — the most common avoidable causes
• Hepatitis B and C tests, if the cause is unclear
• A liver ultrasound scan — to assess fatty liver disease
• Ferritin — to rule out haemochromatosis
• When to repeat the test — a small rise is often followed over time

A low ALT

A low ALT is normal and does not indicate disease. Very low values are sometimes seen in older age or with a vitamin B6 deficiency, but they usually have no clinical significance.

• A normal state — a healthy liver
• Older age, a small muscle mass
• Vitamin B6 deficiency — rarely

Usually nothing needs to be done — a low ALT is not a cause for concern.

ALT and AST

ALT is found mostly in the liver, while AST is found in the liver, in muscle and in the heart. That makes ALT more specific to the liver, and a raised AST can also mean muscle damage. The ratio of the two helps a doctor suggest the cause — in alcoholic liver disease, for example, AST is often higher than ALT.

At the Medicina practica laboratory an ALT test costs from €7 (September 2026 pricing); a liver test panel is priced separately. A family doctor can order the test free of charge when there are indications for it.