Your liver is an organ that plays a role in over 500 functions in your body. You can check your liver function with a blood test. Alcohol, being overweight, an unhealthy diet, and certain medications can affect your liver function.
- What is the liver?
- What is a liver function test?
- What can a liver function test check for?
- Signs and symptoms of liver disorders
- How to test your liver function
- Interpreting your liver function test results
- What affects liver function?
- How to improve your liver function
What is the liver?
The liver is an organ that sits in the upper part of your stomach and is essential for your health. In fact, it plays a role in over 500 functions in your body. These include:
- creating bile acids — help you digest food
- breaking down and storing nutrients
- detoxifying your blood
- fighting infections
- helping your blood to clot
- maintaining hormone balances
- regulating blood sugar levels
What is a liver function test?
A liver function test will measure the levels of a range of things in your blood, like proteins, liver enzymes, and bilirubin. Measuring these things can help check your liver function and also check for signs of inflammation or damage.
The main proteins measured in a liver function test are:
- albumin — helps transport nutrients and hormones, as well as helping grow and repair tissues in your body
- globulin — helps your blood to clot and fights infections
- total protein — this is your albumin and globulin levels combined
The main enzymes measured in a liver function test are:
- alkaline phosphatase (ALP) — helps break down proteins so your body can absorb them
- alanine transferase (ALT) — also helps break down proteins
- gamma-glutamyl transpeptidase (GGT) — helps detoxify drugs and alcohol
Bilirubin is a yellow pigment. When your red blood cells break down, bilirubin is what’s leftover. It’s a waste product with no known function in your body.
What can a liver function test check for?
A liver function test can be used to check for:
- liver infections — for example, hepatitis B and hepatitis C
- non-alcoholic fatty liver disease
- alcohol-related liver disease
- scarring on your liver (cirrhosis)
- gallbladder disease
- possible side effects of medications
Signs and symptoms of liver disorders
The signs and symptoms of a liver disorder might include:
- tiredness and fatigue
- loss of appetite
- weight loss
- low sex drive (libido)
- jaundice — when you have too much bilirubin and it causes yellow skin and eyes and itchy skin
- nausea and vomiting
- abnormal bruising
- abdominal pain
- a build-up of fluid in your abdomen
If you have these symptoms, it’s really important to see your doctor and test your liver function.
How to test your liver function
A blood test is used to check your liver function. You can do this with your GP or using an at-home finger-prick blood test.
Regularly checking your liver function is particularly beneficial if you:
- drink a lot of alcohol — the NHS recommends no more than 14 units a week (roughly 6 pints of beer or 10 small glasses of wine)
- are overweight or obese
- have diabetes
- have high blood pressure
- have high triglyceride levels
- have haemochromatosis — a build-up of iron in your body
If your liver function results are out of range, your doctor might do an ultrasound scan or biopsy to check for liver damage.
Interpreting your liver function test results
Since a liver function test measures many different biomarkers, it can help pick up a wide range of issues. High or low levels of certain proteins and enzymes can indicate that there’s a problem with your liver.
If your liver or kidneys aren’t working properly, it can cause your albumin levels to drop. This might be caused by a poor diet, an infection, kidney disease, or inflammation.
Normal albumin levels range from 34-50 g/L.
Many conditions can cause your globulin levels to increase or decrease. If your globulin levels are high and your albumin levels are low, this can be a sign of liver disease.
Normal globulin levels range from 19-35 g/L.
Low total protein levels can be a sign of a liver or kidney disorder. It might also be a sign that you’re not absorbing food properly — for example, if you have inflammatory bowel disease (IBD) or coeliac disease.
High total protein levels can be a sign of chronic inflammation or an infection like viral hepatitis. It’s rare, but it can also be a sign of a bone marrow disorder or HIV.
Normal total protein levels range from 63-83 g/L.
Alkaline phosphatase (ALP)
High ALP levels can be a sign of liver inflammation, damage to your gallbladder, or bone disease. An ALP level:
- under 104 IU/L is considered normal for men
- under 129 IU/L is considered normal for women
Alanine transferase (ALT)
ALT is mainly only found in your liver, so it’s a good indicator of your liver function. A high ALT level can be a sign of liver damage. An ALT level between:
- 10-50 IU/L is considered normal for men
- 10-35 IU/L is considered normal for women
Aspartate aminotransferase (AST)
AST is an enzyme found mainly in your heart, liver, and muscles. So if your AST levels are raised, it doesn’t necessarily mean it’s a because of a problem with your liver. That’s why it’s important to look at both your AST and ALT levels. High AST levels can be a sign of liver damage.
An AST level under 40 IU/L is considered normal.
Gamma-glutamyl transpeptidase (GGT)
High GGT levels can be a sign of liver damage or disease. If you drink too much alcohol, your GGT levels usually increase.
A GGT level:
- under 71 IU/L is considered normal for men
- under 42 IU/L is considered normal for women
High bilirubin levels can be a sign that your liver is damaged. If you drink excessive amounts of alcohol, take certain medications, or if you are destroying more red blood cells than normal (haemolysis) it can increase your levels. Sometimes it might be caused by Gilbert’s syndrome — a harmless inherited disorder.
A bilirubin level:
- under 24 umol/L is considered normal for men
- under 15 umol/L is considered normal for women
What affects liver function?
How alcohol affects your liver function
Drinking too much alcohol can lead to alcohol-related fatty liver disease (ARLD). This is because heavy drinking damages your liver and stops it from being able to break down fats. If you stop drinking alcohol or lower your intake to a safe level your liver usually repairs itself. If you keep drinking a lot your liver will become inflamed. And over a few years, this can cause permanent scarring on your liver (cirrhosis) and lead to liver failure.
How weight affects your liver function
Being overweight or obese can also cause fatty liver disease, called nonalcoholic fatty liver disease (NAFLD). Other risk factors for NAFLD include:
- high cholesterol or triglycerides
- high blood pressure
- type 2 diabetes
- lack of exercise
Like with ARLD, NAFLD can cause permanent damage to your liver if left untreated for years.
How drugs affect your liver function
Some common over the counter drugs, like acetaminophen (paracetamol) and nonsteroidal anti-inflammatories (aspirin and ibuprofen), can cause serious damage to your liver if you take too much of it in one go or take high doses over a couple of days. These should also never be taken with alcohol or for a hangover until all of the alcohol is out of your system. This is because it interferes with your liver function and can cause very serious side effects, even death.
Other drugs that can affect your liver include:
- antifungal drugs
- antiviral drugs
It’s important to always consult with your doctor when taking any medication. If a possible side effect of the medication is liver damage you should make sure to do regular liver function tests.
How diet affects your liver function
Your diet has a big impact on the health of your liver. The worst foods for your liver include:
- saturated and trans fats — like fried foods, red meat, cakes, pastries, and cream
- refined carbohydrates — like white bread and white pasta
- added sugars — like fruit juices, fizzy drinks, and sweets
- salt — like frozen foods, salted nuts, and smoked or cured meats
How to improve your liver function
The good news is that it usually takes years for permanent liver damage to develop. So if you catch it early enough, there are lots of lifestyle changes you can make so that your liver can repair itself.
To improve your liver function, you should:
- limit the amount of alcohol you have per week to 14 units — that’s equivalent to 6 pints of beer or 7 glasses of wine
- lose weight if you’re overweight or obese
- eat a healthy diet full like a Mediterranean diet
- make sure you get enough exercise — aim for a mix of aerobic and activities
- drink some coffee — research is still limited but some studies have shown that caffeine can help improve your liver function
Recommended listening for you
Harris, E. H. (2005). Elevated liver function tests in type 2 diabetes. Clinical diabetes, 23(3), 115-119.
O'shea, R. S., Dasarathy, S., & McCullough, A. J. (2010). Alcoholic liver disease. Hepatology, 51(1), 307-328.
Park, E. J., Lee, J. H., Yu, G. Y., He, G., Ali, S. R., Holzer, R. G., ... & Karin, M. (2010). Dietary and genetic obesity promote liver inflammation and tumorigenesis by enhancing IL-6 and TNF expression. Cell, 140(2), 197-208.
Smith, B. W., & Adams, L. A. (2011). Non-alcoholic fatty liver disease. Critical reviews in clinical laboratory sciences, 48(3), 97-113.
Thoma, C., Day, C. P., & Trenell, M. I. (2012). Lifestyle interventions for the treatment of non-alcoholic fatty liver disease in adults: a systematic review. Journal of hepatology, 56(1), 255-266.