Liver blood tests: what the results mean

What are liver blood tests?

Liver blood tests are a group of blood tests, once known as liver function tests or LFTs. They can include ALT, AST, ALP, GGT, bilirubin and albumin.

What do ALT and AST show?

ALT and AST are enzymes that leak into the blood when liver cells are injured. ALT is more specific to the liver, while AST can also be high when muscle is damaged elsewhere in the body. Common causes of this pattern include viral hepatitis, non-alcoholic fatty liver disease, alcohol-related liver disease, autoimmune hepatitis and drug-induced liver injury. In alcohol-related liver injury AST is often higher than ALT, whereas in fatty liver disease ALT is often the higher of the two.

What do ALP, GGT, bilirubin and albumin show?

Raised ALP and GGT point towards a problem with the flow of bile. Causes include blocked bile ducts, for example by stones, and some long-term diseases of the bile ducts. ALP also comes from bone, so GGT helps to show whether the liver is the source. Raised bilirubin causes jaundice, a yellowing of the eyes and skin. Bilirubin can also be raised without liver disease, as in Gilbert's syndrome, where the other liver tests are normal. Albumin is affected only when liver disease is at a severe stage, and other factors can also change albumin results. A normal GGT alongside a raised ALP points towards a source other than the liver, such as bone. Bilirubin is a pigment made when red blood cells break down, and the liver normally clears it. Albumin is a protein made by the liver.

Does an abnormal result mean liver disease?

Abnormal results can occur in conditions that do not involve the liver, and normal results can be found in people with serious liver disease. The British Liver Trust says it is very common to have some liver blood test results that are not normal. It also says it is possible to have a normal liver blood test result and still have a serious liver condition. Medicines and herbal supplements can raise liver enzymes, as can some non-liver problems such as muscle injury. Guidelines usually start by repeating the tests, and move to further checks if results stay abnormal.

What happens after an abnormal result?

Laboratories compare each result with their own range, so results are compared only with the range of the laboratory that did the test. If the results suggest a liver problem, a GP may calculate a FIB-4 index, which gives an indication of the amount of scarring in the liver. Depending on the results, age and possible causes, a GP may arrange more tests or regular repeat tests. Further tests can look for the cause, such as viral hepatitis, fatty liver disease or an effect of alcohol or medicines.

When is yellowing of the skin urgent?

The NHS says jaundice can be a sign of something serious such as liver disease. It advises asking for an urgent GP appointment or contacting NHS 111 when the skin or whites of the eyes look yellow. On brown or black skin the yellow colour is easier to see in the whites of the eyes. Itchy skin, darker urine and paler stools can come with it.

What are fatty liver and alcohol-related liver disease?

NHS guidance names non-alcoholic fatty liver disease, in some pathways now called MASLD, as a common cause of abnormal liver tests. NHS hospital guidance says fatty liver disease (MASLD) is treated mainly by reversing its underlying cause, with weight loss a key part. Where alcohol is the cause, one pathway advises cutting out alcohol and repeating the test after a month. Local guidance suggests repeating the tests, including after stopping a medicine that may be affecting the liver. If results stay abnormal, guidance supports an ultrasound scan of the liver and bile ducts and blood tests for viral and autoimmune causes. Local pathways use a FibroScan result, as well as FIB-4, to decide who is referred to a liver clinic. Jaundice can have causes outside the liver, including gallstone disease and the breakdown of red blood cells (haemolysis).