Liver Function Tests (LFT)

When and Why They’re Done

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Our body is like a very complex machine, and each part has a special job. One of the most important and hardworking parts is the liver. Think of it as the body’s super-factory. It cleans our blood, helps digest food, stores energy, and makes important proteins. Because it does so much, it’s crucial to know if it’s working properly. This is where Liver Function Tests come in. These simple blood tests help doctors check the health of your liver and see if there are any problems.

Understanding your health reports can sometimes feel confusing, but it doesn’t have to be. This guide will explain everything about Liver Function Tests in a very simple and easy-to-understand way. We will cover what these tests are, why they are done, what the results mean, and how you can keep your liver healthy. Whether your doctor has recommended an LFT or you are just curious about your health, this article will answer all your questions.

Summary

Liver Function Tests (LFTs) are simple blood tests that show how well your liver is working. They help doctors spot inflammation, blockage, or damage early so treatment can start on time.

ALT and AST go up when liver cells are irritated or damaged—like with hepatitis, fatty liver, or some medicines. Higher numbers don’t always mean severe disease, but they signal “check further.”

Alkaline phosphatase (ALP) and GGT increase when bile can’t flow properly, as in gallstones or alcohol-related issues. Together they point toward blockage vs. bone-related ALP causes.

Bilirubin rises with jaundice. Albumin (a protein) and INR (clotting) reflect the liver’s ability to synthesize—worse values suggest chronic or severe disease and need prompt care.

What Are Liver Function Tests?

Liver Function Tests, often called LFTs, are a group of blood tests that help doctors understand how well your liver is working. Your liver is a vital organ, performing hundreds of essential tasks to keep you healthy. When the liver is damaged or not functioning correctly, it can release certain chemicals called enzymes into the bloodstream. It might also stop producing important substances like proteins. These blood tests measure the levels of these enzymes and proteins in your blood.

By looking at these levels, doctors can get a clear picture of your liver’s health. It helps them diagnose liver diseases, monitor the progress of a treatment, or see how a particular medicine is affecting the liver. It’s a very common and important tool for maintaining your overall health.

The history of Liver Function Tests dates back to the early 1900s when scientists began identifying the liver’s role in chemical metabolism and detoxification. As laboratory medicine evolved, specific enzymes such as Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST) were discovered as key indicators of liver health. Today, LFTs are one of the most common and valuable diagnostic tools in clinical practice, guiding the early detection and management of liver diseases worldwide.

At its core, a Liver Function Test is a screening tool. It involves taking a small sample of your blood, usually from a vein in your arm, and sending it to a lab for analysis. The main purpose of these tests is to measure specific enzymes and proteins.

The key goals of performing Liver Function Tests are:

⦿ Screening for Liver Infections: To check for infections like hepatitis.

⦿ Monitoring Disease Progression: To see if a known liver disease like cirrhosis is getting better or worse.
⦿ Evaluating Treatment: To understand if a treatment for liver disease is effective.
⦿ Checking for Medication Side Effects: Some medicines can affect the liver, and LFTs help monitor this.
⦿ Assessing Liver Damage: To determine the extent of damage or scarring (cirrhosis) in the liver.

Getting an abnormal result from your Liver Function Tests can be worrying, but it doesn’t always mean you have a serious problem. Many things can cause temporary changes in your liver enzyme levels, including some medications, alcohol, or even intense exercise.

An abnormal result is simply a signal for your doctor to investigate further. It means that the levels of certain enzymes or proteins are outside the normal range. For example, high enzyme levels might suggest inflammation or damage to liver cells, while low protein levels could mean the liver’s production function is weak. Your doctor will interpret the results based on your overall health, symptoms, and medical history.

Types of Liver Function Tests

When you get a report for Liver Function Tests, you will see a list of different tests with their results. Each test provides a unique piece of the puzzle about your liver’s health. Let’s look at the most common tests in a bit more detail. To make it easier, you can ask for the liver function tests name from the lab technician or your doctor.

The ALT test measures the level of the enzyme alanine transaminase. This enzyme is mostly found inside your liver cells. When liver cells are damaged, ALT leaks out into your bloodstream. A high ALT level is a very specific indicator of liver inflammation or injury.

The AST test measures the enzyme aspartate transaminase. Like ALT, AST is also found in the liver. However, it is also present in other parts of the body, such as the heart, muscles, and kidneys. Because of this, a high AST level by itself is not as specific for liver damage as a high ALT level. Doctors often look at the ratio of AST to ALT to get more clues about the cause of the liver problem.

The ALP test measures the enzyme alkaline phosphatase. This enzyme is concentrated in the liver, bile ducts, and bones. High ALP levels can indicate a problem with the liver or, more specifically, a blockage in the bile ducts. Since it’s also found in bones, doctors might run other tests to confirm if the problem is coming from the liver.

Bilirubin is a yellow substance that your body creates during the normal process of breaking down old red blood cells. The liver is responsible for processing bilirubin and removing it from the body. High levels of bilirubin can cause jaundice, which is the yellowing of the skin and eyes. The test measures both total bilirubin and direct bilirubin to help pinpoint the cause of the problem.

This test measures the amount of protein in your blood, especially albumin, which is made by the liver. Albumin is crucial for many body functions, like preventing fluid from leaking out of blood vessels. If your liver is severely damaged, it may not be able to produce enough albumin, leading to low levels in the blood. Sometimes, people might see a liver function test high protein result, which could also indicate certain health conditions that your doctor will investigate.

The GGT test measures the enzyme gamma-glutamyl transferase. This enzyme is very sensitive to changes in liver function. GGT levels can be elevated due to many types of liver problems, but they are particularly sensitive to issues caused by alcohol consumption or blocked bile ducts. It is often used in combination with other tests like ALP to confirm liver-related issues.

Test Name	What It Measures	What Abnormal Levels Might Mean
Alanine Transaminase (ALT)	An enzyme primarily found in the liver.	High levels strongly suggest liver cell damage or inflammation (e.g., from hepatitis).
Aspartate Transaminase (AST)	An enzyme found in the liver, heart, and muscles.	High levels can indicate liver damage, but also issues with other organs.
Alkaline Phosphatase (ALP)	An enzyme found in the liver, bile ducts, and bones.	High levels often point towards blocked bile ducts, gallstones, or certain liver diseases.
Bilirubin	A waste product from the breakdown of red blood cells.	High levels can cause jaundice and may indicate problems with the liver's ability to process waste.
Albumin	A key protein made by the liver.	Low levels can signal chronic liver disease or cirrhosis, as the liver's ability to produce protein is reduced.

Why Are Liver Function Tests Done?

Doctors recommend Liver Function Tests for several important reasons. These tests are a window into the health of one of your body’s most essential organs. They are not just for people who are already sick; they can be a part of routine health care to catch problems before they become serious. Understanding why these tests are done can help you appreciate their value in maintaining your long-term health.

One of the most important reasons to perform Liver Function Tests is for the early detection of liver disease. Many liver problems, like fatty liver disease or chronic hepatitis, may not show any obvious symptoms in their early stages. A person could feel completely fine while their liver is slowly getting damaged. An LFT can pick up on subtle signs of trouble, like slightly elevated enzymes, long before symptoms appear. This early warning allows doctors to intervene with lifestyle changes or treatment, potentially preventing severe and irreversible liver damage.

For individuals who have already been diagnosed with a liver condition such as hepatitis C, alcoholic liver disease, or cirrhosis, regular Liver Function Tests are essential. These tests help the doctor monitor the state of the disease. They can see if the condition is stable, getting worse, or responding well to treatment. For example, if a patient is on medication for hepatitis, a decrease in their ALT and AST levels would be a positive sign that the treatment is working effectively. This monitoring helps in adjusting treatment plans for the best possible outcome.

Before prescribing certain medications, a doctor might order Liver Function Tests. This is because many drugs are processed by the liver. Some medications, including common ones for cholesterol, tuberculosis, or even some painkillers, can potentially harm the liver, especially in people with pre-existing liver issues. By checking the liver’s health beforehand, the doctor can ensure it is safe to start the medication. They may also perform follow-up LFTs to make sure the drug is not causing any negative effects on the liver.

Many people get Liver Function Tests done as part of their annual or routine health checkup. This is a proactive approach to health. Since the liver is so vital and liver problems can be silent, a routine LFT can provide valuable reassurance that everything is okay. It can also be an opportunity to identify risk factors. For instance, if the results are slightly off, a doctor might discuss lifestyle factors like diet, alcohol intake, and exercise to help prevent future problems.

Symptoms That May Require an LFT Test

Your body often sends signals when something is wrong. While some liver problems are silent, many eventually cause noticeable symptoms. If you experience any of the following signs, your doctor will likely recommend Liver Function Tests to check what’s happening with your liver. It’s important to pay attention to these symptoms and consult a healthcare professional.

Jaundice is one of the most well-known signs of a liver problem. It happens when there is too much bilirubin in your blood. As we discussed, bilirubin is a yellow pigment, and when it builds up, it can make your skin, the whites of your eyes, and even your mucous membranes turn yellow. Jaundice is a clear indicator that the liver is not processing bilirubin correctly, which could be due to hepatitis, blocked bile ducts, or other serious liver conditions.

Changes in the color of your urine and stool can also be a warning sign. When the liver is working properly, it helps remove bilirubin through the stool, which gives it a normal brown color. If the liver is not functioning well or the bile ducts are blocked, bilirubin can build up and be excreted through the kidneys instead. This can make your urine very dark, almost like tea or cola. At the same time, your stool might become very pale, clay-colored, or gray because of the lack of bilirubin.

Feeling unusually tired all the time is a common but non-specific symptom of many health issues, including liver disease. This persistent fatigue is not relieved by rest. You might also experience nausea, vomiting, or a general loss of appetite. Another common symptom is pain or discomfort in the upper right side of your abdomen, which is where your liver is located. This pain can be a dull ache or a sharp, stabbing sensation.

If you are losing weight without trying, it could be a sign that something is wrong. A poorly functioning liver can affect your digestion and appetite, leading to unintentional weight loss. Another significant symptom is swelling, particularly in your legs, ankles, and abdomen. This condition, known as edema and ascites, occurs when a damaged liver can’t produce enough albumin, causing fluid to leak from blood vessels and accumulate in body tissues.

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How to Prepare for Liver Function Tests

Preparing for your Liver Function Tests is usually very simple, but following the instructions given by your doctor or the lab is important to ensure the results are accurate. A few simple steps can make a big difference in the quality of the test outcome. Most of the preparation involves being mindful of what you eat and drink before the test.

One of the most common questions people ask is, “liver function test do you need to fast?” The answer is often yes. Your doctor might ask you to fast, which means not eating or drinking anything (except water) for about 8 to 12 hours before the test. The liver function test time for sample collection is usually in the morning after an overnight fast. This is because the nutrients in food and drinks can be absorbed into your bloodstream and temporarily affect the levels of certain substances, potentially leading to inaccurate results. So, the question of whether a liver function test require fasting is best answered by your doctor.

Before your test, it’s crucial to inform your doctor about all the medications you are taking. This includes prescription drugs, over-the-counter medicines, and even herbal supplements. Some medicines can affect your liver enzyme levels. Your doctor will tell you if you need to temporarily stop taking any medication before the test. You should also avoid drinking alcohol for at least 24 to 48 hours before your LFT, as alcohol can cause a temporary spike in liver enzymes and interfere with the results.

Having an open conversation with your doctor about your health history and lifestyle is also a part of the preparation. Tell them about any existing medical conditions, your diet, exercise habits, and alcohol consumption. This information helps the doctor interpret the results of your Liver Function Tests more accurately. For instance, if you’ve recently had a viral infection or engaged in strenuous exercise, it could affect the results, and knowing this context is helpful for a proper diagnosis.

Normal Ranges of Liver Function Tests

After your blood sample is analyzed, you will receive a report with the results. This report will show the levels of different enzymes and proteins and compare them to a “normal range.” Understanding what these numbers mean is key, but it’s essential to remember that interpreting these results should always be done by a qualified doctor. The ranges can vary slightly between different liver function tests labs.

The normal range, or reference value, is the range of levels considered healthy for most people. Your report will likely show your result next to this range. If you are looking for a liver function tests chart, you will find that these values can differ based on the lab, the technique used, and factors like age and gender.

Here are some typical reference values:
⦿ ALT (Alanine Transaminase): 7 to 55 units per liter (U/L)
⦿ AST (Aspartate Transaminase): 8 to 48 U/L
⦿ ALP (Alkaline Phosphatase): 40 to 129 U/L
⦿ Total Bilirubin: 0.1 to 1.2 milligrams per deciliter (mg/dL)
⦿ Albumin: 3.5 to 5.0 grams per deciliter (g/dL)

While you can look at the numbers, the real liver function tests results interpretation must be done by your doctor. They will not just look at a single high or low number in isolation. Instead, they will analyze the entire pattern of the results. For example, the ratio of AST to ALT can provide clues about the cause of liver damage.

Your doctor will also consider your symptoms, medical history, and a physical examination to form a complete picture. You might find a liver function tests interpretation pdf online, but it cannot replace a professional medical opinion.

Values are generally considered alarming when they are significantly outside the liver function test normal values. For instance, if your liver enzymes like ALT or AST are several times higher than the upper limit of the normal range, it indicates a more serious level of liver inflammation or damage. Similarly, very low albumin levels combined with high bilirubin can be a sign of advanced liver disease. Your doctor will explain if your liver function tests levels are a cause for concern and what the next steps should be.

Test Parameter	Typical Normal Range	Potential Meaning of High Levels	Potential Meaning of Low Levels
ALT	7 - 55 U/L	Liver cell damage (hepatitis, fatty liver, drug injury).	Generally not a concern.
AST	8 - 48 U/L	Liver damage, muscle injury, or heart problems.	Generally not a concern.
ALP	40 - 129 U/L	Blocked bile ducts, gallstones, bone disorders.	Malnutrition, zinc deficiency (rare).
Total Bilirubin	0.1 - 1.2 mg/dL	Liver disease, bile duct blockage, Gilbert's syndrome.	Generally not a concern.
Albumin	3.5 - 5.0 g/dL	Inflammation, shock, malnutrition. (A liver function test total protein high result might indicate other issues).	Chronic liver disease (cirrhosis), kidney disease, malnutrition.

Causes of Abnormal Liver Function Test Results

If your LFT report shows that your liver function tests raised, you might wonder about the cause. There are many potential reasons for abnormal results, ranging from temporary and harmless issues to more serious underlying diseases. Your doctor will conduct a thorough investigation to determine the specific liver function test high causes.

Viral hepatitis is a common cause of liver inflammation and damage, leading to abnormal LFT results. Viruses like Hepatitis A, B, and C directly attack liver cells. This causes a significant increase in liver enzymes, particularly ALT and AST. A specific panel of tests for liver function tests hepatitis can be done to confirm which virus is causing the infection. Hepatitis A is usually a short-term illness, while Hepatitis B and C can become chronic and lead to long-term liver damage if not treated.

Excessive and long-term alcohol consumption is a major cause of liver damage. It can lead to alcoholic fatty liver, alcoholic hepatitis, and eventually cirrhosis. Regular use of alcohol will almost certainly lead to abnormal results in liver function tests for alcohol abuse, especially with elevated GGT and an AST/ALT ratio greater than 2:1.

Another very common condition is non-alcoholic fatty liver disease (NAFLD), where fat builds up in the liver even in people who drink little to no alcohol. This is often linked to obesity, diabetes, and high cholesterol.

Cirrhosis is a late-stage condition where healthy liver tissue is replaced by scar tissue, permanently damaging the liver. This scarring prevents the liver from working properly. It is often the result of long-term damage from conditions like chronic hepatitis or alcohol abuse. The LFT results in cirrhosis can be complex, sometimes showing very high enzymes and sometimes even normal or low levels as the number of healthy liver cells decreases. Liver cancer can also cause highly abnormal Liver Function Tests.

Many different medications can potentially harm the liver. This is known as drug-induced liver injury (DILI). It can be caused by prescription drugs, over-the-counter medicines (like paracetamol if taken in very large doses), or even some herbal and dietary supplements. If a medication is causing liver inflammation, the LFTs will show elevated enzyme levels. Your doctor will review your medications to see if one of them might be the cause of the problem.

Follow-Up After Abnormal LFTs

Receiving abnormal results from your Liver Function Tests is just the first step. The next step is to find out why the results are abnormal. Your doctor will likely recommend further tests to get a more detailed look at your liver and determine the exact cause of the problem. This helps in creating an effective treatment plan.

After an abnormal LFT, one of the most common follow-up steps is an imaging test. These tests create pictures of your liver and surrounding organs.

⦿ Ultrasound: This uses sound waves to create images and is very good for detecting issues like fatty liver, cysts, tumors, or problems with the gallbladder, such as liver function tests gallstones.

⦿ CT Scan (Computed Tomography): This provides more detailed, cross-sectional images of the liver and can help identify tumors or other structural abnormalities.

⦿ MRI (Magnetic Resonance Imaging): This uses magnets and radio waves to produce very detailed images and is excellent for examining soft tissues and bile ducts.

In some cases, the doctor might need to examine a small piece of your liver tissue directly. This is done through a liver biopsy. A thin needle is used to take a tiny sample of the liver, which is then examined under a microscope. This can help determine the exact type and extent of liver damage.

A less invasive alternative is a FibroScan. This is a special type of ultrasound that measures the stiffness of the liver. A stiffer liver usually means more scarring (fibrosis or cirrhosis), and this test can help assess the level of damage without a biopsy.

Once the cause of the abnormal LFT is identified, treatment can begin. This often involves a combination of lifestyle changes and medications.

⦿ Lifestyle Changes: Your doctor will likely advise you to stop drinking alcohol, lose weight if you are overweight, eat a healthy diet, and get regular exercise. These changes can significantly improve liver health, especially in cases of fatty liver disease.

⦿ Medications: Depending on the diagnosis, you may be prescribed medications. For example, antiviral drugs are used to treat chronic hepatitis B or C. Other medicines might be used to manage symptoms or complications of liver disease.

Preventing Liver Problems

Taking care of your liver is one of the best things you can do for your overall health. Many liver problems can be prevented by adopting a healthy lifestyle. Prevention is always better than cure, and these simple steps can help keep your liver functioning at its best, ensuring your liver function tests normal range stays consistent.

What you eat has a direct impact on your liver. A healthy, balanced diet can help prevent conditions like fatty liver disease.

⦿ Eat Plenty of Fruits and Vegetables: They are rich in antioxidants, which protect liver cells from damage.

⦿ Choose Whole Grains: Foods like oats, brown rice, and whole-wheat bread are high in fiber, which helps the liver.

⦿ Include Lean Protein: Opt for fish, chicken, beans, and lentils.

⦿ Drink Coffee: Some studies suggest that moderate coffee consumption can be good for the liver.

⦿ Stay Hydrated: Drink plenty of water throughout the day.

Some things are particularly hard on your liver and should be limited or avoided.

⦿ Alcohol: Alcohol is a toxin that your liver has to process. Excessive drinking is a leading cause of liver damage.

⦿ Processed Foods: Foods high in sugar, salt, and unhealthy fats (like fast food, packaged snacks, and sugary drinks) can contribute to fat buildup in the liver and cause inflammation

⦿ Saturated and Trans Fats: Limit your intake of red meat and fried foods.

Getting regular health checkups, which include Liver Function Tests, is a great way to monitor your liver health, especially if you have risk factors like diabetes, obesity, or a family history of liver disease. Regular checkups can help catch any issues early when they are most treatable. Your doctor can guide you on how often you should get tested based on your individual health profile.

You can protect your liver from viral hepatitis by getting vaccinated. Vaccines are available for Hepatitis A and Hepatitis B. Practicing good hygiene, such as washing your hands thoroughly, is also important to prevent the spread of Hepatitis A. To avoid Hepatitis B and C, never share needles, razors, or toothbrushes, and ensure any tattoos or piercings are done with sterile equipment.

Foods to Include for a Healthy Liver	Foods to Limit or Avoid	Why It Matters
Oatmeal, Brown Rice, Whole Grains	Sugary Sodas, Packaged Snacks, Sweets	Fiber helps with digestion and reduces stress on the liver. High sugar can lead to fat buildup in the liver.
Broccoli, Spinach, Leafy Greens	Fried Foods, Fast Food	These vegetables are packed with antioxidants that protect the liver from damage. Unhealthy fats cause liver inflammation.
Garlic, Onions, Turmeric	Excess Salt, Canned Soups, Processed Meats	These contain compounds that help the liver detoxify the body. High salt intake can lead to fluid retention and strain the liver.
Green Tea, Coffee (in moderation)	Alcohol, Beer, Wine	Antioxidants in these beverages may help reduce the risk of liver disease. Alcohol is a direct toxin to liver cells.
Lean Protein (Fish, Chicken, Beans)	Red Meat, Full-Fat Dairy	Provides essential amino acids without adding excessive saturated fat. Saturated fats contribute to fatty liver disease.

Frequently Asked Questions

What are liver function tests?

Liver function tests, or LFTs, are simple blood tests that help check the health of your liver. They measure the levels of certain proteins and enzymes in your blood. These levels tell doctors how well your liver is doing its job.

What do liver function tests show?

These tests show if your liver is inflamed, injured, or not working properly. They measure substances that the liver releases when it's damaged or substances it fails to produce when it's sick. This gives a good picture of your overall liver health.

Why is a liver function test done?

A doctor may ask for an LFT to find the cause of symptoms like jaundice or stomach pain. It is also done to check for liver damage from infections, alcohol, or medicines. The test helps monitor treatment for liver diseases as well.

How long does it take to get liver function test results?

Getting your LFT results is usually very quick. Most labs provide the report within 12 to 24 hours. Your doctor's clinic will inform you once the results are ready to be discussed.

What does it mean if liver function test results are abnormal?

Abnormal results mean that some levels are higher or lower than the normal range. This could be a sign of liver stress or a potential liver problem. Your doctor will explain what your specific results mean for your health.

Can a liver function test detect liver diseases like hepatitis or cancer?

Yes, LFTs can show strong signs that suggest diseases like hepatitis or cancer. However, they cannot confirm the diagnosis alone. Your doctor will use these results to decide if other tests, like an ultrasound or biopsy, are needed.

How can I interpret liver function test results?

It is always best to let your doctor interpret your results. They will look at the entire report, not just one number, along with your symptoms and medical history. Self-interpretation can be misleading and cause unnecessary worry.

What causes liver function test results to be high or abnormal?

High results can be caused by many things, including infections like hepatitis, fatty liver disease, and drinking too much alcohol. Certain medicines, and even some herbal products, can also cause your liver enzyme levels to go up.

How can I lower high liver function test results?

You can help lower high results by eating a healthy, balanced diet and avoiding fatty or junk food. It is also very important to limit or stop drinking alcohol and to maintain a healthy weight through regular exercise. Always follow your doctor's advice for the best results.

Dr. Harsh Shah

MS, MCh (GI cancer Surgeon)

Dr Harsh Shah is a well known GI & HPB Robotic Cancer Surgeon in ahmedabad. He treats cancers of esophagus, stomach, liver, pancreas, colon, rectum & small intestines. He is available at Apollo Hospital.

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Liver Function Tests (LFT)

When and Why They’re Done

When and Why They’re Done

Summary

What Are Liver Function Tests?

Types of Liver Function Tests

Why Are Liver Function Tests Done?

Symptoms That May Require an LFT Test

Consult OncoBot

How to Prepare for Liver Function Tests

Normal Ranges of Liver Function Tests

Causes of Abnormal Liver Function Test Results

Follow-Up After Abnormal LFTs

Preventing Liver Problems

Frequently Asked Questions

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