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Plain-language information for patients

What is a liver function test?

Liver function tests (LFTs) are a group of blood tests that give a picture of how your liver is doing. Despite the name, some of them reflect liver injury or bile flow rather than 'function' itself.

What the main results mean

ALT and AST are enzymes released when liver cells are irritated or damaged (for example by fatty liver, alcohol, viruses or some medicines). ALP and GGT relate more to the bile ducts. Bilirubin is the pigment that causes jaundice when high, and albumin and clotting reflect the liver's working capacity.

Mildly abnormal LFTs are very common and often have a simple explanation. The pattern of which tests are raised helps point to the cause.

What happens next?

Depending on the pattern and your history, your doctor may repeat the tests, ask about alcohol and medicines, arrange a scan (such as an ultrasound), or check for viral hepatitis and other causes.

Persistently abnormal results, or signs of more serious liver disease, prompt further investigation and sometimes specialist referral.

Common questions

Are mildly abnormal liver tests serious?

Usually not by themselves — they are common and often due to things like fatty liver. But they should be followed up to find the cause and to check they are not getting worse.

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This page is general information, not personal medical advice, and does not replace a consultation with a qualified health professional. If you are worried about your health, please speak to your GP, pharmacist, or another clinician. Last reviewed 2026-06-08.