“Your liver tests are slightly raised” is one of the most common things people hear after a blood test, and one of the most confusing. Liver blood tests are often abnormal, and most abnormal results are mild. But they are also an early warning sign that is easy to ignore, because liver problems rarely cause symptoms until they are advanced.

What liver blood tests measure

“Liver function tests” is a slightly misleading name. Most of them measure enzymes and substances that leak into the blood when liver cells are irritated or damaged:

• ALT (alanine aminotransferase) is the most liver-specific enzyme. A raised ALT usually means liver cells are under strain.
• GGT (gamma-glutamyl transferase) is often raised by alcohol, fat in the liver and some medicines.
• ALP (alkaline phosphatase) comes from the liver and bile ducts, but also from bone, so it needs interpreting carefully.
• Bilirubin is a breakdown product of red blood cells. A mildly raised level on its own is often due to Gilbert’s syndrome, a common and harmless inherited condition.
• Albumin is a protein made by the liver, and gives a sense of how well the liver is working overall.

The most common causes

Fat in the liver. The most common cause of raised liver tests in the UK is fatty liver disease, now often called MASLD (metabolic dysfunction-associated steatotic liver disease). It is closely linked to carrying extra weight around the middle, type 2 diabetes, high blood pressure and raised cholesterol, and it often goes unnoticed for years.

Alcohol. Regularly drinking above the recommended 14 units a week can raise GGT and ALT, often well before any other sign of harm.

Medicines and supplements. A number of prescribed medicines, over-the-counter painkillers and herbal or bodybuilding supplements can affect the liver.

Less common causes include viral hepatitis, iron overload (haemochromatosis), coeliac disease, thyroid problems and autoimmune liver conditions. A doctor will consider these based on your history and the pattern of your results.

Why it matters

Most people with mildly raised liver tests will never develop serious liver disease. But in some, ongoing inflammation leads to scarring (fibrosis) over many years, which can eventually progress to cirrhosis. The important point is that the early stages can improve, and in fatty liver disease they can reverse completely.

Signs of liver strain were one of the main modifiable findings in our audit of health checks.

What you can change

• Lose weight if you are carrying extra. Losing around 7 to 10% of body weight can significantly reduce fat in the liver.
• Cut down on alcohol, and have several alcohol-free days each week.
• Move more, which reduces liver fat even before weight changes.
• Cut down on sugary drinks and highly processed food.
• Review medicines and supplements with your doctor.

What happens after a raised result

A single mildly raised result is usually repeated after a few weeks or months, often after lifestyle changes, to see whether it settles. If it stays raised, your doctor will look for the cause with further blood tests. Where fatty liver is suspected, a simple score called FIB-4, calculated from routine blood results and your age, helps estimate the risk of scarring and whether further tests, such as a specialist scan, are needed.

Both our Core and Advanced Health Checks include a full liver profile. Your doctor reviews every result in the context of your history, explains it in your personal results report, and books a dated repeat test if one is needed.