Your liver is one of the busiest organs in the body — it processes nutrients, filters toxins, makes proteins and helps with digestion. A liver function test (LFT) is a group of blood markers that together give a snapshot of how the liver is doing. The name is slightly misleading: some of the markers reflect liver damage rather than function, but read together they are a valuable early-warning system.
The markers in a liver function test
A standard panel usually includes:
- ALT and AST — enzymes found inside liver cells. When cells are irritated or damaged, these leak into the blood, so raised levels point to liver stress.
- ALP (alkaline phosphatase) — an enzyme linked to the bile ducts and also to bone; raised levels may suggest a bile-flow issue, among other causes.
- GGT — often rises alongside ALP and is sensitive to alcohol and some medicines, helping clarify the source of an ALP rise.
- Bilirubin — a yellow pigment the liver processes; high levels can cause jaundice.
- Albumin and total protein — proteins the liver makes, reflecting its longer-term working capacity.
What raised enzymes suggest
Because different markers point to different parts of the liver's work, the pattern matters more than any single figure. Raised ALT and AST tend to reflect irritation of the liver cells themselves, while raised ALP and GGT lean towards the bile-drainage side. A doctor reads these together to work out where attention is needed.
Common reasons for abnormal results
There are many causes, and plenty are not serious:
- Fatty liver — increasingly common, linked to weight and metabolic health.
- Alcohol — can raise GGT and other markers.
- Medications and supplements — some can nudge liver markers up.
- Recent illness or vigorous exercise — can cause temporary changes.
- Viral hepatitis and other liver conditions — less common but important to identify.
Check your liver
A liver function test measures the key markers of liver health — ALT, AST, ALP, GGT, bilirubin and proteins — in one blood draw.
Check your liverWhat to do with the results
Mildly abnormal liver results are frequently picked up and often settle on their own or improve with lifestyle changes. The key is not to panic over a single reading but to have it interpreted in context and, where advised, repeated. Persistent or marked abnormalities may prompt further tests, such as viral screening or an ultrasound, guided by a clinician.
When to get checked
A liver test can be worthwhile if you drink more than you would like, are carrying extra weight, take regular medication, or have symptoms such as unexplained fatigue, upper-abdominal discomfort or yellowing of the skin or eyes. It is also a sensible part of a general health check. If results come back abnormal, follow them up with a clinician rather than self-diagnosing.
Check your liver
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Specialist interest: Cardiovascular Medicine · OneMedicine, CQC-registered clinic