In short: A liver function test (LFT) is a common blood test that measures enzymes and proteins linked to the liver, such as ALT, ALP, GGT, bilirubin and albumin. Abnormal results can point to liver inflammation, bile duct problems or other conditions, but mildly raised results are common and need interpreting alongside your history. Importantly, normal LFTs do not rule out liver disease, including fatty liver disease and early scarring.

This guide, written by a Ready Health prescribing pharmacist in Standish, Wigan, explains what an LFT measures, why it might be done and what results can and cannot tell you.

What does a liver function test measure?

Despite the name, most of an LFT measures signs of liver cell damage or bile flow rather than how well the liver is working. A typical liver profile includes:

Marker	What it mainly reflects
ALT (alanine aminotransferase)	Damage or inflammation in liver cells
AST (aspartate aminotransferase)	Liver cell damage; also found in muscle and the heart
ALP (alkaline phosphatase)	Bile duct problems; also comes from bone, and is naturally higher in pregnancy and in growing children
GGT (gamma-glutamyl transferase)	Bile duct problems; often raised by alcohol and some medicines
Bilirubin	A yellow pigment processed by the liver; high levels cause jaundice
Albumin	A protein made by the liver; low levels can reflect long-term liver disease, poor nutrition or other illness

Exact panels vary between laboratories and providers, so check what is included before booking.

Why might you need a liver function test?

Symptoms such as yellowing of the skin or eyes, dark urine, pale stools, persistent itching, or unexplained tiredness or tummy pain
Monitoring while taking medicines that can affect the liver
Regular alcohol use above the UK low-risk guideline of 14 units a week
Risk factors for fatty liver disease, such as type 2 diabetes or living with obesity
Follow-up of a previous abnormal result or a known liver condition such as viral hepatitis

If you develop yellowing of the skin or eyes, see a GP the same day or call NHS 111. If you are very unwell, confused or vomiting blood, call 999.

What do abnormal results mean?

Mildly abnormal LFTs are common and often caused by alcohol, excess weight, medicines or recent illness. Common causes of abnormal results include:

fatty liver disease linked to weight, diabetes or metabolism (now often called MASLD)
alcohol-related liver disease
viral hepatitis (for example hepatitis B or C)
medicines and some herbal or bodybuilding supplements
gallstones or other bile duct blockage
less common conditions such as haemochromatosis (iron overload) and autoimmune liver disease

A single abnormal result is not a diagnosis. Depending on the pattern, a clinician may repeat the test, ask about alcohol and medicines, arrange further blood tests (a liver screen) or an ultrasound scan, and assess the risk of liver scarring.

Can normal LFTs miss liver disease?

Yes. Liver disease often has no symptoms until it is advanced, and blood tests can be normal even when there is fatty liver or significant scarring (fibrosis). For people at higher risk, UK guidance recommends specific fibrosis assessment, such as a calculated FIB-4 score using routine blood results, followed where needed by an enhanced liver fibrosis (ELF) blood test or a specialised scan.

How do you prepare for a liver function test?

It is a standard blood sample from a vein in the arm.
Fasting is not usually needed for an LFT alone, but may be needed if other tests are taken at the same time. You will be told when you book.
Tell the clinician about all medicines, supplements and alcohol intake, as these affect interpretation.
Avoid very strenuous exercise the day before, as it can raise some enzymes.

Frequently asked questions

Can an LFT tell me if I have fatty liver?

Not reliably. LFTs can be normal in fatty liver disease. Diagnosis usually involves risk assessment, imaging and fibrosis scoring.

Will alcohol affect my results?

Yes, particularly GGT. Be honest about how much you drink so your results can be interpreted properly.

What happens if my result is abnormal?

A clinician will review it with your symptoms and history, and may recommend repeat or further tests, or advise you to see your GP for ongoing care.

Can I improve my liver test results?

Often, yes. Reducing alcohol, losing excess weight, staying active and reviewing medicines with a clinician can improve results in many people. Do not stop prescribed medicines without advice.

Key takeaways

LFTs mainly show liver cell damage and bile flow, not overall liver function.
Mildly abnormal results are common and need clinical interpretation.
Normal LFTs do not rule out fatty liver or liver scarring.
Jaundice needs same-day medical advice.

Sources and further reading

Last reviewed: October 2026 by Shamir Patel, Independent Prescribing Pharmacist, Ready Health. This article is general information and does not replace advice from your own clinician.

If you would like a liver profile as part of a private blood test, see our private blood tests in Standish, Wigan. If any result is abnormal, you can discuss it at a private GP appointment or with your own GP.