Non-alcoholic fatty liver disease (NAFLD) has become one of the most common liver conditions in the UK, and its rise mirrors that of obesity and type 2 diabetes. As the name suggests, it involves a build-up of fat in the liver in people who drink little or no alcohol. The tricky part is that it is often completely silent in its early stages — many people have no symptoms at all — which is why blood tests play such a useful role in spotting it.
What is happening in the liver
In NAFLD, fat accumulates within liver cells. For many people this stays mild and stable. In others it can progress to inflammation and, over years, to scarring (fibrosis) and more serious liver damage. Catching it early matters because the earlier stages are often reversible with lifestyle changes, before lasting harm is done.
What liver blood tests reveal
A liver function test measures a set of markers that reflect how the liver is doing. In fatty liver disease, certain patterns can appear:
- ALT and AST — enzymes released when liver cells are irritated or damaged. Mildly raised levels are a common first clue to fatty liver.
- GGT — another liver enzyme that can be elevated and helps build the picture.
- ALP, bilirubin, albumin and protein — these round out the assessment of how the liver is functioning overall.
It is worth knowing that liver blood tests can be normal even when some fat is present, so a normal result does not completely exclude fatty liver — it is one part of the assessment.
The metabolic connection
Fatty liver rarely travels alone. It is closely linked with carrying excess weight (particularly around the middle), insulin resistance and type 2 diabetes, raised triglycerides and high blood pressure. Because of this, doctors often look at the wider metabolic picture — including HbA1c and a lipid profile — rather than the liver in isolation. Improving these areas tends to improve the liver too.
Check your liver
A liver function test measures ALT, AST, GGT, ALP, bilirubin and albumin — the markers that can flag early signs of fatty liver and prompt a fuller look at your metabolic health.
Book a liver testWhat comes after the bloods
If liver tests are raised, the next step is usually to look for a cause and to gauge how much fat and scarring is present. This can include an ultrasound scan and sometimes specialised tests that estimate liver stiffness. Your doctor will also want to exclude other causes of abnormal liver tests, such as alcohol, medications and viral hepatitis, so the bloods are a springboard rather than a final answer.
What helps — and when to see a doctor
The mainstay of managing fatty liver is lifestyle: gradual weight loss where appropriate, a balanced diet lower in refined sugar, regular physical activity, and keeping alcohol within safe limits or avoiding it. See a doctor promptly if you develop yellowing of the skin or eyes (jaundice), unexplained weight loss, swelling of the tummy or legs, vomiting blood, or persistent right-sided tummy pain — these warrant prompt assessment. Otherwise, mildly abnormal liver tests are best discussed calmly with a clinician who can put them in context.
Check your liver
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Specialist interest: Cardiovascular Medicine · OneMedicine, CQC-registered clinic