Liver Function Test – Everything You Need to Know

The liver is one of the most important organs in the body and has more than 500 individual functions1, many crucial to staying healthy. In this post, we will learn about the liver and also systematically breakdown each and every test done as part of a typical Liver Function Test (LFT).

Why is it important to get a liver function test?

Most liver functions revolve around metabolic activity. Metabolic activities are chemical reactions that occur to make or break down components2. This includes some crucial bodily functions like:

  • Metabolizing nutrients2
  • Creating proteins2
  • Breakdown of toxins within the blood2
  • Storing vitamins3
  • Storing fats3
  • Maintaining hormone levels3
  • Producing blood clotting factors3
  • Producing bile3
Bile is a fluid made and released by the liver. It is important for digestion.

A badly functioning liver can have an extremely harmful effect on the body, resulting in serious health conditions. Liver diseases cause 3.5% of all deaths globally. This equates to 2 million people dying from liver disease each year4.

Despite the potential for liver complications to have serious health effects, these conditions build up gradually. The warning signs can be seen in smaller symptoms. However, considerable damage might have already been done at this point5. Thus, liver function tests are important to monitor your liver for any diseases that could be developing.

What does a liver function test measure?

A liver function test consists of several different blood tests obtained via the same blood sample3. Here’s what it typically tests for:

Alanine Aminotransferase (ALT)

Alanine Aminotransferase (ALT) is an enzyme in the liver that is released into the bloodstream when the liver is damaged.

An enzyme is a substance that helps a chemical reaction occur within the body.
What is ALT's role in the body?

ALT is present in large quantities in the liver. It is also present in smaller amounts in the kidneys, heart and muscles3. ALT is involved in processes that provide our cells with energy6. ALT takes alanine from proteins and breaks it into pyruvate and glutamate which provide cells with the energy they require for functioning6.

What does an abnormal ALT result mean?

At normal levels, ALT is a part of a process that provides energy to cells. However, when a liver cell dies due to liver damage, the contents of that cell enter the bloodstream. The ALT levels in liver cells are much higher than the amounts in kidneys, heart, and muscles. Thus in the scenario of damage to liver cells, the ALT levels in the bloodstream rise significantly and may point to liver damage.

There are other reasons that can contribute to elevated ALT levels too.

  • The liver aids in processing drugs as they are seen as toxins. Introducing a new drug into the body causes ALT levels to rise until the body becomes familiar with it6.
  • Additionally, strenuous exercise can raise ALT levels due to damage to muscle cells3. The level of increase depends on many factors including your sex, duration of exercise, and physical condition7. Moderate exercise will, however, decrease ALT levels7. People who routinely exercise have lower ALT levels in general7.

Aspartate Aminotransferase (AST)

Aspartate aminotransferase (AST) is another enzyme in the liver that is released into the bloodstream when the liver is damaged.

What is AST's role in the body?

AST is present in the liver and the heart3. It is also present in muscles3. The enzyme is involved in processes that provide cells with energy6.

What does an abnormal AST result mean?

Similar to ALT, this enzyme is found in the blood in large quantities when liver cells die and are absorbed into the bloodstream. However, the body breaks down and extracts AST faster than ALT6. This means that AST levels are lower than ALT when there is liver damage.

Here are some factors affecting AST levels in the body:

  • Strenuous exercise7
  • Heart damage/cardiac cell damage7
  • A high number of red blood cells dying within the blood.3

Total Bilirubin

Total bilirubin tests the amount of bilirubin in your body. Bilirubin is a breakdown product of haemoglobin, which causes red blood cells to be red3.

What is Bilirubin's role in the body?

Bilirubin is a waste product created when haemoglobin is broken down3. Normally red blood cells will be functional for 4 months3. After this, they become inefficient and break down. This is when bilirubin is created and is carried to the liver by proteins3.

What does an abnormal Total Bilirubin result mean?

Blood conditions like haemolytic, sickle cell or pernicious anaemias cause excessive red blood cell destruction. This causes abnormally higher levels of bilirubin in the blood3.

Bilirubin has a strong orange-yellow pigment3. This is why when there are high levels of bilirubin in the blood, light coloured body features get a yellow tinge. This is called jaundice and shows up mainly in the whites of your eyes and skin3.

Another way bilirubin levels are increased in the bloodstream can be due to a transfusion causing a negative reaction, increasing the amount of red blood cells being broken down3.

Conjugated Bilirubin

This test only checks the amount of bilirubin made by the liver. The liver processes bilirubin by attaching sugar to it which is called conjugated bilirubin3.

What is Conjugated Bilirubin's role in the body?

Conjugated bilirubin is excreted into bile which travels to the intestines3. Bilirubin is then broken down by the digestive system’s bacteria3. In effect, this is what colours the faeces and how we excrete bilirubin out of our bodies3.

What does an abnormal Conjugated Bilirubin result mean?

As the liver creates and processes conjugated bilirubin, abnormal levels indicate liver complications or disease. Here are some factors that increase conjugated bilirubin levels:

  • Liver conditions like hepatitis and cirrhosis3.
  • Processing of excessive toxins due to long-term alcohol abuse or a new drug3.
  • Blockages within the liver or bile duct3.

Total Protein

This is a blood test that measures the amount of proteins in your blood.

What is protein's role in the body?

There are over 200,000 different types of proteins in the body that all have important individual roles8. This test counts the two important groups of proteins; albumin and immunoglobulin/globulin8.

What does an abnormal Total Protein result mean?

The liver creates a major share of the body’s proteins. Insufficient protein levels can have knock-on effects on quite a few body functions. This can create several side effects and further damage different areas of the body. Learn more about this in our post on the total protein test.

Albumin

Albumin is one of the two main types of proteins that are present in blood.

What is albumin's role in the body?

This type of protein is found in the bloodstream and controls the fluid levels within cells. Albumin also transports nutrients, drugs and hormones throughout the body8.

What does an abnormal Albumin result mean?

The liver produces albumin and controls its levels. If the liver is damaged, albumin levels are reduced and become evidence of liver damage. Learn more about this in our post on the total protein test.

Alkaline Phosphatase (ALP)

Alkaline Phosphatase (ALP) is an enzyme that is made by the liver and is present in bile to help break down fats in your diet.

What is Alkaline Phosphatase's role in the body?

The role of ALP within the body is not specifically known. However, four types have been identified: intestinal, placenta, germ cell and bone/kidney/liver9. ALP has been observed to be part of several cell processes including cell growth, natural cell death and protein creation9.

What does an abnormal Alkaline Phosphatase result mean?

Despite limited knowledge about its role, the ALP blood test assesses blocked ducts and bile ducts within the liver3. ALP levels are checked alongside other liver function tests. Together, they point to any potential evidence of liver damage3. Alternatively, raised ALP levels are used as a monitoring tool for cancer patients who have bone or liver cancers3.

Gama-glutamyl Transferase (GGT)

Gama-glutamyl transferase (GGT) is an enzyme made in the liver that is released into the bloodstream when the liver is damaged. It is the first enzyme to be released and is used for early detection of liver damage3.

What is the role of Gama-glutamyl transferase (GGT) in your body?

GGT is an enzyme and is a part of many important processes10. These include the regeneration of vitamins C & E, neutralising some toxins, regulating cell death and cell repopulation and assisting in creating cellular energy11.

What does an abnormal Gama-glutamyl transferase (GGT) result mean?

Since GGT is found in liver cells, it isn’t normally found in significant levels within the bloodstream. When there are elevated levels of GGT, this is due to increased liver cell death and therefore liver damage3. When GGT is present in the bloodstream, it can damage the red blood cells.

At ElevateMe, we perform the liver function test to monitor your overall liver health through the following tests:

  • Bilirubin
  • Alanine Transferase (ALT)
  • Gamma GT (GGT)
  • Alkaline Phosphatase (ALP)
  • Total Protein
  • Albumin

What are the symptoms of poor liver health?

Unfortunately, when symptoms occur from liver disease, the liver is already scarred12. This is a condition called cirrhosis.

You should get a liver function test when you experience any of the following symptoms of cirrhosis:

  • Feeling tired constantly
  • Feeling weak in general
  • Loss of appetite – this may lead to weight loss
  • Reduced libido
  • Being frequently itchy
  • Experience any yellowing of the skin or whites of the eyes – known as jaundice
  • Muscle wasting
  • Abdominal pain13.

Cirrhosis is the first instance of any liver disease, however if the condition causes damage to the liver where it cannot function, this is then caused liver failure.

Signs of liver disease do include side effects that are mainly generalised. But there are a few side effects that point only to liver issues. These include:

  • Being frequently itchy,
  • Jaundice- yellowing of the skin or the whites of your eyes,
  • Pale looking stool,
  • Becoming easy to bruise and bleed,
  • Becoming constantly bloated,
  • Darker coloured urine14.

If you experience any of these side effects over a significant period, it is important to get a liver function test. Once identified, liver disease and declining liver health can be improved before permanent long term damage.

What lifestyle habits affect liver health?

There are 4 main causes of developing liver disease. To ensure you are promoting the best environment for liver health, it is important to put steps in place to avoid these causes.

Alcohol Consumption - Leads to Alcohol Related Liver Disease (ARLD)

This is the onset of liver disease due to long term excessive alcohol consumption. ARLD follows the same course as most liver diseases. It does not show any symptoms until the liver is severely damaged15.

When the liver processes alcohol, there is a small number of liver cells that actually die15. The liver can regenerate these lost cells. However, liver damage will occur if the amount of cells lost is greater than the rate at which the liver can replace them. Damage is reversible with early diagnosis by stopping alcohol consumption for at least two weeks15.

To ensure that ARLD is not developed, it is important to ensure that your alcohol consumption is at a safe level. Make sure you do not exceed consuming 14 units of alcohol a week. Furthermore, avoid binge drinking by spreading out weekly alcohol consumption over 3 days or more15.

Spotting ALRD early is the best way to treat liver damage. And liver damage can only be identified through a liver function test.

Non-alcohol related fatty liver disease (NAFLD)

NAFLD is a condition where fat deposits around the liver make it unfunctional15. People with the following conditions are at a higher risk of developing NAFLD:

  • Overweight (particularly around the waist)
  • Type 2 Diabetes
  • High blood pressure
  • High cholesterol levels
  • Metabolic syndrome – A combination of diabetes, high blood pressure and obesity
  • Over the age of 50
  • Addiction to smoking15

The symptoms of NAFLD present themselves in the later stages of the condition. They are not necessarily liver-specific. With increasing damage to the liver, the symptoms of cirrhosis can be noticed15.

Lack of Hygiene - May cause Viral Hepatitis

Hepatitis is a viral disease which has 5 different types:

  • Hepatitis A: Caused by faecal contamination of food by someone who has hepatitis A. For this reason, it is commonly seen in poor countries with bad sanitation and lack of clean water16.
  • Hepatitis B: Transmits through blood contamination of an infected person. A common transmission is between pregnant women and their children, and also among children under close contact16.
  • Hepatitis C: This is the most common viral strain of hepatitis. It is spread through blood-to-blood contamination such as sharing razors or bad injection practices16.
  • Hepatitis D: This is a progression of hepatitis B. It can also spread via blood or sexual contact16.
  • Hepatitis E: Caused by the consumption of raw or undercooked pork, offal, boar, venison and shellfish16.

It is important to ensure that you practice good hygiene practices to contain the spread of these different types of viral hepatitis.

Drug related Hepatitis

One of the roles of the liver is to remove toxins from the blood. However, the liver can get damaged due to those toxins causing inflammation16. If these toxins originate from medical drugs, the inflammation is called drug-related hepatitis17.

There are three types of drug related hepatitis17:

  • Hepatitis: Originates from poisoning, statism and drugs like paracetamol. It causes high AST and ALT levels.
  • Cholestasis: Originates from medications such as chlorpromazine, erythromycin and oestrogen. It causes high alkaline phosphate levels.
  • Mixed: This is where the medication causes two abnormal results due to increased levels of aminotransferases and alkaline phosphatase, both liver enzymes.

Treatment for these conditions is to stop the medication causing the damage17. Once the medication has been halted, management of the remaining symptoms is then carried out if not immediately gone.

Are there people more at risk for liver disease?

Unfortunately, yes. People at higher risk for liver disease include:

  • Prolonged alcohol abusers14
  • Males14
  • Type 2 Diabetics14
  • Age > 50 years14
  • BMI > 3013

What are the normal ranges for a liver function test?

Although these are the normal ranges for liver function tests, most have a wide range. At ElevateMe, we have identified optimal areas for these ranges as shown below. Optimal levels are the values that you should target as they highlight the ranges of healthy and thriving individuals. Optimal ranges tell you the numbers that will allow you to live an optimum life. This is in contrast to reference ranges where the numbers just tell you that you are not sick. Here’s a post on the differences between optimal and reference ranges in blood tests and why we use the former for the ElevateMe program.

Blood TestNormal Reference Range18Optimal Range
Bilirubinless than 21 IU/L6.83-21 IU/L
ALT15-45 IU/L17-30 IU/L
GGT11-55 IU/L15-65 IU/L
ALP30-130 IU/L30-80 IU/L
Albumin35-50 g/L44-55 g/L
Total Protein60-80 g/L60-83 g/L

What should you do if you have abnormal liver health?

If you have abnormal liver function test results, it is important to seek medical advice. Especially if you are not aware of any abnormal side effects. This will ensure that any potential liver conditions are spotted early.

How can you improve liver health?

The main factors that will aid in improving your liver health are a well-balanced diet and good exercise levels19.

Physical Exercise

Obesity is a high-risk factor for developing liver conditions13. Thus, if your Body-Mass Index (BMI) is high, it would be beneficial to try to lose weight and lower it. As a matter of fact, reducing your BMI score by 5% will in turn reduce your liver fat by 25%20.

Exercise will trigger your body to burn more energy which it can gain from triglycerides21. Triglycerides increase due to an unhealthy diet. The liver stores excess calories in the form of triglycerides22. Limiting calorie intake to recommended values will reduce strain on the liver. Moreover, this will reduce the body’s overall fat percentage. Consequently, this will reduce the likelihood of having excess fat on the liver23.

Here’s a tool to calculate your daily recommended calorie intake and your BMI.

Diet

Some foods reduce the likelihood of developing liver conditions. These include:

  • Coffee24
  • Grapefruit25
  • Blueberries 25
  • Grapes25
  • Banana26
  • Figs26
  • Lemon26
  • Barley26
  • Omega 3 fatty acid supplements27

Most importantly, try to avoid unnecessary toxins such as excessive alcohol and drugs. Especially when your liver function is not well balanced. This will reduce excess harm to the liver whilst it is unwell.

Frequently Asked Questions about Liver Function Test

Q. Can a liver function test detect cancer?
A. No. Liver function tests can be used to monitor cancers if they directly affect the liver, but will not be able to diagnose cancer specifically.

Q. Can a liver function test detect hepatitis?
A. Yes. Liver functions can indicate that there is hepatitis present. However, medical imagery is also needed alongside inflammation blood test to diagnose the condition exclusively.

Q. Can a liver function test detect fatty liver
A. Yes. A liver function test will show liver damage caused by fatty liver. However, imagery is also needed to diagnose the condition exclusively.

Q. Can liver function test detect cirrhosis?
A. Yes. A liver function test will show the damage caused by cirrhosis, however further testing will be needed to understand what type of cirrhosis is occurring.

Q. Can a liver function test detect HIV?
A. No. Although HIV affects the liver, a different blood test is used to diagnose HIV.

Q. Can a liver function test detect pregnancy?
A. No. Pregnancy can cause stress to many of the mother’s organs, including the liver, however, abnormal liver results are not able to identify pregnancy specifically.

Q. Can a liver function test detect hepatitis C?
A. No. Although hepatitis causes liver disease and complications in the liver, the type of hepatitis can not be diagnosed through liver function tests.

Did you know? 

According to the latest survey by the UK government, there were 26,265 premature deaths due to liver disease in England, with mortality rates of premature alcoholic liver disease significantly higher in males than for females. 

Take an ElevateMe blood test today to capture 21 blood test insights including liver health and track your sleep, fitness, energy, metabolism, cognition, mood, and immunity.

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References

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2 Waugh, A (2018). Anatomy and Physiology in Health and Illness. 13th ed. London: Elsevier.

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4 Asrani, S., Devarbhavi, H., Eaton, J. & Kamath, P. (2019). Burden of liver diseases in the world. Journal of Hepatology. 70 (1), 151-171.

5 NHS Scotland. (2020). Liver Disease. Last accessed 15/06/2021.

6 Aulbach, A. & Amuzie, C. (2017). Chapter 17 – Biomarkers in Nonclinical Drug Development. In: Faqi, A. A comprehensive guide to Toxicology in Nonclinical Drug Development. 2nd ed. London: Elsevier. 447-471.

7 Kazmierczak, A. & Azzazy, H (2014). Diagnostic Enzymology. 2nd ed. Berlin: Walter de Grutyer.

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11 Pizzorno, J. (2014). Glutathione! Integrative Medicine: A Clinicians Journal. 13 (1), 8-12.

12 NHS. (2020). Liver Disease. Last accessed 15/06/2021.

13 NICE. (2018). When should I suspect Cirrhosis?. Last accessed 15/06/2021.

14 National Institute of Diabetes, Digestive and Kidney Diseases. (2018). Symptoms & Causes of Cirrhosis Last accessed 15/06/2021.

15 NHS. (2018). Non-alcoholic fatty liver disease (NAFLD). Last accessed 15/06/2021.

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18 Levick, C. (2017). How to interpret liver function tests. South Sudan Medical Journal. 10 (2), 40-43.

19 Marchesini, G., Petta, S. & Grave, R. (2015). Diet, weight loss, and liver health in non-alcoholic fatty liver disease: Pathophysiology, evidence, and practice. Hepatology. 63 (6), 2032-2043.

20 Patel, N., Doycheva, I., Peterson, M., Hooker, J., Kisselva, T., Schnabl, B., et al. (2015) Effect of weight loss on magnetic resonance imaging estimation of liver fat and volume in patients with non-alcoholic steatohepatitis. Clinical Gastroenterol Hepatology; 13: 561‐ 568.

21 Moini, J. (2019). Anatomy and Physiology for Health Professionals. 3rd ed. Burlington, USA: Jones & Barlett. 402-508; 626-688.

22 Heart UK. (N.D.) Triglycerides. Last accessed 04/04/201.

23 Marchesini, G. & Mazzotti, A. (2015). NAFLD incidence and remission: only a matter of weight gain and weight loss? Journal of Hepatology; 62: 15‐ 17.

24 Torres, D. & Harrison, S. (2013). Is It Time to Write a Prescription for Coffee? Coffee and Liver Disease. Gastroenterology. 144 (4), 670-672

25 Madrigal-Santillan, E., et al . (2014). Review of natural products with hepatoprotective effects. World Journal of Gastroenterology. 20 (40), 14787-14804.

26 Guan, Y-S. & He, Q. (2015). Plants Consummation and Liver Health. Evidence-Based Complementary Alternative Medicine, ID: 824184.

27 Lu, W., Li, S., Li, J., Wang, J., Zhang, R., et al. (2016). Effects of Omega-3 Fatty Acid in Non-alcoholic Fatty Liver Disease: A Meta-Analysis. Gastroenterology Research and Practice, id: 1459790.

Liver Function Test - ElevateMe

Written by Louise Taylor

After completing Clinical Technology at the University of Bradford, I am venturing into the NHS as a General Medical Engineer.

18/06/2021

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