What high AST/ALT means and whether you need more tests

What each value tells you

AST and ALT are enzymes inside liver cells. When liver cells are inflamed or damaged, these enzymes leak into the blood. ALT is more specific to the liver, while AST is also found in muscle and can rise after heavy exercise or muscle injury.

ALP and GGT relate more to the bile ducts and commonly rise with cholestasis. GGT is also particularly sensitive to alcohol and certain medicines.

Common causes of raised liver values

Frequently seen causes include fatty liver linked to weight and metabolic factors, alcohol use, certain medicines or supplements, and viral hepatitis.

• Fatty liver in people who are overweight or have diabetes or high lipids
• Regular alcohol use, often with a raised GGT
• Some medicines and supplements, including certain herbal products
• Hepatitis B or C infection
• Strenuous exercise the day before testing, which can raise AST temporarily

How doctors assess it

Doctors interpret raised values with your history, weight, conditions, medicines and the AST to ALT ratio, plus bilirubin and albumin, to judge whether the liver is functioning normally.

For mild elevations the usual approach is to review medicines, stop alcohol, reduce weight and repeat the test in 1-6 months. Larger or persistent elevations may lead to further tests such as abdominal ultrasound or viral hepatitis testing.

What you can do yourself

Weight reduction, dietary changes, cutting alcohol, avoiding unnecessary medicines or supplements, and controlling glucose and lipids can improve liver values in many cases.

Always tell your doctor about supplements and herbal products, because many affect the liver and should not be continued when values are raised without a clear cause.