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Abnormal liver function tests (LFTs)

Liver function tests are blood tests that check how well your liver is working

Doctor dressed in white lab coat in one hand holds figure of liver or hepar in another twisted steth
Liver function tests, also known as LFTs or liver blood tests, are a group of blood tests to check the health of your liver. They measure a range of chemicals that can show how well your liver is working and whether there is any damage, disease, or inflammation (abnormalities).

You may have liver function tests as part of a routine blood test if your doctor suspects liver damage, or to monitor a known medical condition.

The liver is the largest internal organ in the body. It is situated above the stomach on the upper right side of the abdominal cavity and performs hundreds of vital functions including:

  • Cleans the blood of toxins
  • Makes a substance called bile that helps digest food
  • Produces substances that help your blood to clot
  • Stores glucose (as glycogen) and vitamins
  • Regulates the amount of blood in the body
  • Breaks down old red blood cells
  • Metabolises carbohydrates, fat and proteins so your body can use them

Liver function tests check for a range of abnormalities in the levels of enzymes, proteins and other substances made by the liver. Tests may be looked at on their own, or in conjunction with other tests to give an indication of inflammation or disease.

Abnormal liver function tests often return to normal within a few weeks, and one abnormal result may not mean you have liver damage. If more than one of your results is abnormal, if you show symptoms of liver disease or if your liver function tests remain high, your doctor may arrange further tests to find out the cause.

Abnormal liver function tests may be caused by:

  • Liver inflammation due to infection, excess alcohol consumption, some medical conditions, or medications
  • Damage to liver cells caused by alcohol, toxins, poisons, or medications like paracetamol
  • Blocked bile ducts
  • Liver abscess
  • Liver tumour
  • Injury to the liver due to trauma
  • Medical conditions that affect liver function

The main liver function tests are:

  • Alanine aminotransferase (ALT)
  • Aspartate aminotransferase (AST)
  • Bilirubin
  • Alkaline phosphatase (ALP)
  • Gamma-glutamyl transferase (GGT)
  • Albumin
  • Total protein
  • Prothrombin time (PT) and international normalised ratio (INR)

Alanine aminotransferase (ALT) and aspartate aminotransferase (AST)

These are enzymes found in liver cells that leak into the bloodstream when cells are damaged. High levels of ALT and AST indicate liver disease or inflammation.

Mild increases may indicate:

  • Non-alcoholic fatty liver disease
  • Chronic hepatitis-C infection
  • Autoimmune hepatitis
  • Haemochromatosis - an inherited condition where there is a build-up of iron in the body
  • Coeliac disease

Severe increases may indicate:

  • Acute alcoholic hepatitis
  • Viral hepatitis A, B, C, D, or E
  • Chronic hepatitis
  • Chronic liver cirrhosis
  • Ischaemic liver damage secondary to serious illness
  • Toxic injury to the liver caused by poisons or medicines


Bilirubin is produced when the body breaks down red blood cells. The liver then processes (conjugates) bilirubin so it can be excreted via the bile ducts through the kidneys. High levels of bilirubin can cause jaundice, where the skin and the whites of the eyes have a yellowish tint.

Conjugated bilirubin is bilirubin that has already been processed by the liver. You may have high levels of conjugated bilirubin if your liver is processing bilirubin correctly, but it isn't being excreted properly via the bile ducts. This may be caused by:

  • Blockage of the bile ducts, such as by a gallstone
  • Adverse reactions to some medications
  • Some autoimmune diseases
  • Inherited conditions such as Dubin-Johnson syndrome and Rotor syndrome
  • In babies, a rare defect in the bile drainage system

High levels of unconjugated bilirubin indicate that either your liver can't process bilirubin, or that your body is making too much bilirubin for your liver to process effectively. Some causes of elevated unconjugated bilirubin include:

  • Gilbert's syndrome - a harmless, hereditary condition where the liver cannot process bilirubin properly
  • Increased haemolysis (destruction of red blood cells) caused by congenital blood defects, reactions to medications, infections, and some diseases

A rise in conjugated and unconjugated bilirubin may occur if there is both damage to the liver and problems with the drainage of bilirubin.

Alkaline phosphatase (ALP)

ALP is an enzyme found in the bile duct and elevated levels may indicate a blocked or damaged bile duct. These may be due to:

  • Gallstones
  • Hepatitis
  • Cirrhosis
  • Blocked bile ducts
  • Bone damage or disease

Gamma-glutamyl transferase (GGT)

This liver enzyme is a sensitive marker that rises in most liver disease and may also be elevated in some conditions affecting the heart, lungs, and kidneys. Raised GGT levels may be caused by:

  • Excessive alcohol consumption
  • Non-alcoholic fatty liver disease
  • Chronic hepatitis C infection
  • Some medications
  • In chronic liver disease, bile duct damage and scarring


Albumin is a protein made by the liver that is important for tissue growth and repair. Low albumin levels may indicate:

  • Severe liver disease or inflammation
  • A condition that affects your body's absorption of protein such as celiac disease or Crohn's disease
  • A condition where protein leaks through the bowel wall like severe bowel inflammation or infection
  • Protein loss due to kidney problems
  • Loss of protein through the skin due to severe burns or skin inflammation
  • Dilution of albumin in the blood due to pregnancy
  • Poor nutrition

Total protein

Total protein measures the total albumin and globulins. High total protein is seen in:

  • Chronic active hepatitis
  • Alcoholic hepatitis
  • An increase in globulins due to conditions such as myeloma (a type of blood cancer), infections and chronic inflammation

Low levels of total protein may be due to:

  • Severe liver disease
  • Conditions causing loss of protein like burns, or bowel or kidney disease
  • Poor nutrition

Prothrombin time (PT) and international normalised ratio (INR)

These tests measure your blood's ability to clot. PT and INR may be increased in:

  • Acute liver disease
  • Liver failure
  • Paracetamol overdose
  • Use of blood thinning medications

At your first consultation, you will be seen by a consultant gastroenterologist, a doctor specialising in conditions affecting the digestive system. Your consultant will ask about any symptoms you have, your general health, and lifestyle and perform a physical examination.

Your first appointment is important as it's where we get to know you, discuss your expectations for treatment, and encourage you to ask any questions you may have.

At Circle Health Group we want you to be as well-informed and comfortable as possible during your time with us, so please feel free to discuss any concerns and ask any questions during your appointment.

Information about how to prepare for your liver function tests will be in your hospital appointment letter. To ensure your results are accurate, follow these instructions carefully and call the hospital if you have any questions.

Tell your doctor about any medical conditions you have, and medications, including over-the-counter medicines, and supplements you are taking. You may need to stop eating and drinking for eight to twelve hours before the test.

Liver function tests involve taking a small amount of blood from a vein. The blood is taken by a health professional, usually a nurse, or a person called a phlebotomist who is specially trained to take blood.

Tell the person taking your blood if you are particularly anxious, or feel lightheaded, dizzy, or sick at any time while you are having your blood taken. It may help to look away and focus on something else or take deep breaths while your blood is being taken. From start to finish, the process only takes a few minutes.

To perform liver function tests:

  1. The skin is cleaned where the blood will be taken. This is normally from a vein in the middle of your arm
  2. A rubber band called a tourniquet will be tightened around your upper arm to make your vein easier to access. You may be asked to make a fist
  3. A needle is inserted into a vein and blood is drawn out with a syringe
  4. The tourniquet and needle are removed
  5. You will be asked to press a swab over the area where the blood was taken for a few minutes. This is to prevent bleeding and bruising

A liver function test is a safe and minimally invasive procedure that does not normally result in complications. You may have some bruising and your arm may feel sore for a couple of days after the blood test.

Your doctor will advise you on what happens next if your liver function tests are abnormal. This may include:

  • Repeating the liver function test in a few weeks
  • Further blood tests to try to find out the cause of your abnormal result
  • Further liver imaging tests or liver biopsy
  • Treatment if a diagnosis is made

We answer some of your most commonly asked questions about liver function tests.

Do gallstones cause abnormal liver function tests?

Yes. Acute cholecystitis (inflammation of the gallbladder) and gallstones can cause the liver enzymes alkaline phosphatase (ALT) and aspartate transaminase (AST) to be elevated.

Do abnormal liver function tests make you feel unwell?

Abnormal liver function tests do not normally make you feel unwell, and you can have abnormal results without having any symptoms.

Common symptoms of liver damage, inflammation, or disease include:

  • Poor appetite
  • Nausea
  • Vomiting
  • Fatigue
  • Yellowing of the skin or the whites of the eyes (jaundice)
  • Dark-coloured urine
  • Clay-coloured poo
  • Abdominal pain and swelling
  • Itching of the skin

How do I know if my alcohol intake is affecting my liver?

Alcohol-related liver disease (ARLD) often doesn't show symptoms until your liver is badly damaged. The liver enzyme gamma-glutamyl transferase (GGT) is currently the most reliable marker for excessive alcohol use and rises after prolonged heavy drinking. It normally falls back to within normal limits after a couple of weeks of abstinence.

If you are worried about your alcohol intake, talk to a health professional. They can discuss how much you are drinking, provide advice and support on how to cut down and arrange for tests to check your liver function if needed.

How can I prevent liver damage?

It isn't always possible to prevent damage to your liver, but there are some things you can do to improve the health of your liver and reduce the risk of liver disease.

  • If you drink alcohol, stick to safe limits (no more than fourteen units a week with two to three consecutive alcohol-free days per week)
  • Follow a healthy balanced diet
  • Get vaccinated against hepatitis A and B
  • Keep your weight within healthy limits
  • Take regular exercise

At Circle Health Group we have the experience and expertise to ensure the best possible care and outcome for our patients. As a patient with Circle Health Group, you can expect the highest standards of care including:

  • Flexible appointment times and locations that are convenient for you
  • The freedom to choose which hospital and consultant suit your needs
  • Personalised, consultant-led treatment plans tailored to your individual needs
  • Comfortable and safe private facilities maintained by expert multidisciplinary teams
  • Private ensuite rooms as standard
  • A range of delicious healthy meals
  • Affordable, fixed-price packages with aftercare included
  • Flexible payment options to help you spread the cost of your care

If you would like to see a consultant or learn more about liver function tests, book your appointment online today or call a member of our team directly on 0141 300 5009.

Content reviewed by Circle in-house team in February 2023. Next review due February 2026.

  1. Liver blood tests (Formerly known as liver function tests – LFTs), British Liver Trust
  2. Abnormal Liver Function Tests, Patient
  3. Liver Function Tests, NIH
  4. Evaluation of abnormal liver function tests, BMJ Journals

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