Abnormal liver blood test: what does it mean?

Your liver is a large cone-shaped organ that sits in the upper right area of your abdomen. It is responsible for a wide variety of functions, from making bile, hormones and enzymes, and filtering and detoxifying your blood, to processing digested food, and storing iron, vitamins and minerals. When your liver isn’t working properly, you can, therefore, experience a wide variety of symptoms. 

A liver blood test, formerly known as a liver function test, can help check the health of your liver and identify potential liver problems. It measures the levels of enzymes, proteins and other substances in your blood that are made by your liver and its bile ducts (tubes that transport bile out of your liver).

Types of liver blood tests

Depending on your symptoms, your GP may refer you for particular liver blood tests. There are four main liver blood tests:

1. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) test

These are enzymes in your liver cells that can leak into your bloodstream if your liver is inflamed or damaged. High ALT and AST levels occur during liver infections (hepatitis) and also during liver scarring (fibrosis).

2. Albumin test

This protein is made by your liver cells and makes up around 60% of the proteins found in your blood. It is needed to transport hormones and nutrients around your body but if your liver is damaged, your albumin levels can drop. 

3. Alkaline phosphatase (ALP) and y-Glutamyltransferase (GGT) test

These are enzymes in the bile ducts of your liver. The level of enzymes in your bloodstream increases if there is blockage of these ducts eg if you have obstructive cholestasis. GGT levels can also be raised if you have non-alcohol-related fatty liver disease (NAFLD) or drink excessive amounts of alcohol. 

4. Bilirubin test

This protein is made when your red blood cells are broken down and is what makes your bile a yellow-green colour. High levels of bilirubin cause jaundice and can suggest that you have liver disease. 

Healthy levels of each of these proteins and enzymes fall within different, specified ranges. Anything outside of these ranges, whether that is higher or lower, is considered an abnormal liver blood test and can suggest liver damage or disease, depending on your other symptoms and medical history. 

Is an abnormal liver blood test serious?

How serious your liver condition is depends on how abnormal the results of your liver blood test are. In most cases where the results are not significantly beyond healthy ranges, the condition is not serious but does need investigation and potential treatment. 

If you receive an abnormal liver blood test, your doctor will explain your results to you and what they mean in your particular case. If needed, they will refer you to a doctor who specialises in treating liver disease (a hepatologist), and recommend further tests such as an ultrasound scan, CT scan or MRI scan.

Common causes for an abnormal liver blood test

In the UK, there are several common causes for an abnormal liver blood test. 

The most common cause is alcohol-related liver disease (ARLD). This is where drinking excessive amounts of alcohol over years causes fat to build up in your liver. This leads to alcoholic fatty liver disease, which can be reversed if steps are taken to stop drinking. If not, this progresses to alcoholic hepatitis and eventually liver cirrhosis, where your liver becomes scarred and can no longer work properly. 

Non-alcohol-related fatty liver disease (NAFLD) also causes fat to build up in your liver but is not caused by drinking excessive amounts of alcohol. Instead, it is caused by several risk factors including being overweight, having poorly controlled diabetes, metabolic syndrome, high cholesterol and/or high blood pressure. 

Other conditions that can cause an abnormal liver blood test include bile duct stones, where your bile duct becomes blocked with gallstones that have moved out of the gallbladder, and viral hepatitis, where the liver is infected with a virus and becomes inflamed. 

Certain medications and herbal supplements can also produce an abnormal liver blood test by causing drug-induced liver injury (DILI). 

Treating liver disease, damage and injury

Treatment of your liver condition will depend on the underlying cause and the severity of your condition.

ARLD is treated by stopping drinking alcohol, while NAFLD requires lifestyle changes to reduce your risk factors eg losing excess weight, controlling diabetes and following a healthier diet to reduce high blood pressure and/or high cholesterol.

If you have DILI, changing medication is usually enough to allow the liver to recover.

Viral hepatitis can be caused by infection with different hepatitis viruses and consequently, treatment depends on which virus you have been infected with. It may only involve rest, staying hydrated and following a healthy diet, or you may need to take an antiviral drug.

Bile duct stones are usually removed using a minimally invasive procedure called an endoscopic retrograde cholangiopancreatography (ERCP). This is where a thin, flexible telescope-like tube with a light and camera on the end (endoscope) is inserted via your mouth into a part of your small intestine called the duodenum, which your bile duct opens into. Small surgical instruments can be passed via the endoscope to help remove the bile duct stones.

How to maintain a healthy liver

As with all health conditions, prevention is better than cure. To avoid developing a liver condition, it is important to quit smoking, exercise regularly (at least 30 minutes of moderate exercise every day), avoid drinking more than 14 units of alcohol per week, and follow a healthy, balanced diet low in saturated and trans fats.