Liver Function Test (LFTs) – When is it done, Preparation and Procedure

Liver function tests are blood analyses designed to assess the health of your liver. Also referred to as liver chemistries, liver function tests evaluate liver health by measuring proteins, liver enzymes, and bilirubin levels in your blood. They can also track the progression or effectiveness of treatment for an existing condition.

Depending on the specific test, atypically high or low levels of these enzymes or proteins may suggest an issue with your liver.

There are various reasons for conducting liver function tests, including screening for conditions like hepatitis, monitoring potential side effects caused by medications, and assessing the extent of liver disease. This article explores when a liver function test might be necessary, the types of tests available, and how to interpret the results.
 

When is a liver function test recommended?

A liver function test is commonly advised in the following circumstances:

1. To assess potential damage from liver infections such as hepatitis B and hepatitis C, 

2. Particularly if there’s a suspicion of exposure to a hepatitis-causing virus.

3. To track the side effects of certain medications that can impact liver health, including:

• NSAIDs
• statins
• antibiotics
• antiseizure drugs
• tuberculosis treatments

4. If you have an existing liver disease, monitor its progression and the effectiveness of specific treatments.

5. If you show symptoms of a liver disorder or have a family history of liver illnesses, like fatty liver disease.

6. If you have particular medical issues, including:

• high triglyceride levels
• diabetes
• hypertension
• anaemia
• if you frequently consume alcohol
• if you suffer from gallbladder disease

Different tests can indicate varying aspects of liver function. For instance, elevated levels of alanine transaminase and aspartate transaminase that are disproportionate to bilirubin and alkaline phosphatase often suggest liver disease. Consult your doctor for any necessary preparation steps. In certain situations, you may be required to refrain from eating or taking specific medications before the test.
 

Suggested Timeline

• Every 6 months: If you are at higher risk (e.g., with existing liver conditions, high alcohol consumption, or frequent medication use).
• Yearly: As a preventive measure to ensure liver health in individuals without significant risk factors.
   

What types of liver function tests are available?

Liver function tests are used to quantify specific enzymes and proteins present in your blood. Having abnormal results on any of these liver tests typically necessitates a follow-up to identify the underlying cause of these irregularities. Even slightly elevated levels can be linked to liver disease.
 

Common liver function tests encompass:

1. Alanine transaminase (ALT) test

Your body utilises alanine transaminase (ALT) for protein metabolism. If the liver becomes damaged or malfunctions, ALT can leak into the bloodstream, increasing ALT levels. A result exceeding the normal range on this test may indicate liver damage.

2. Aspartate aminotransferase (AST) test

Aspartate aminotransferase (AST) is an enzyme present in various organs, including your:

• heart
• brain
• pancreas
• liver
• muscles

When liver damage occurs, AST can escape into the blood. A high AST result may suggest an issue with the liver or muscles. Because AST is not as specific for liver damage as ALT, it is usually measured alongside ALT to assess liver health. For instance, a high AST: ALT ratio could indicate alcoholic liver disease.

3. Alkaline phosphatase (ALP) test

Alkaline phosphatase (ALP) is an enzyme in your bones, bile ducts, and liver. An ALP test is commonly ordered alongside several other tests. It can be used to evaluate the liver's bile duct system.

4. Bilirubin examination  

Bilirubin is a byproduct of the breakdown of red blood cells. Typically, the liver processes it, subsequently eliminating it through stool. If the liver is damaged, it cannot effectively process bilirubin, resulting in elevated bilirubin levels in the bloodstream. Certain genetic conditions may raise bilirubin levels even when liver function is normal.  
 

Understanding liver function test results  

Interpreting liver function test results  

After undergoing a liver function test, discussing the outcomes with your doctor is important. Here’s a concise overview:

1. ALT Test  

Elevated Levels: This may indicate liver injury. Levels exceeding 1,000 U/L are frequently associated with viral hepatitis, ischemic hepatitis, or damage from medications.  

Normal Range: Below 25 IU/L for females and 33 IU/L for males.  

2. AST Test  

Elevated Levels: This can suggest liver, heart, or muscle issues. Isolated elevation of AST may point to heart or muscle disorders. If it appears together with high ALT, bilirubin, or ALP, it could imply liver damage.  

Normal Range: Up to 36 U/L for adults.  

3. ALP Test  

Elevated Levels: This might indicate liver inflammation, obstruction of bile ducts, or bone diseases. Levels might naturally be elevated in children and pregnant individuals.  

Normal Range: 20–140 IU/L for adults.  

4. Albumin Test  

Low Levels: This may indicate inadequate liver function, as seen in cirrhosis, cancer, or malnutrition. Low levels can also stem from kidney issues or infections.  

Normal Range: 35–50 g/L.  

5. Bilirubin Test  

Elevated Levels: Indicate potential liver issues such as cirrhosis or hepatitis, particularly when ALT or AST is also elevated.  

Normal Range: 0.1–1.2 mg/dL.  

Always depend on your doctor's interpretation for precise diagnosis and treatment.  
 

What are the signs of a liver condition?  

Liver issues can cause significant illness and can even pose a life-threatening risk.  

Signs of a liver condition include:  

• weakness  
• fatigue or decreased energy  
• unintentional weight loss  
• jaundice (yellowing of the skin and eyes)  
• fluid accumulation in the abdomen, termed ascites  
• discoloured bodily waste (dark urine or pale stools)  
• nausea  
• vomiting  
• diarrhoea  
• abdominal discomfort  
• unusual bruising or bleeding  

If you experience symptoms of a liver condition, your doctor might request a liver function test. Liver function tests can also be used to track the advancement or treatment of an illness and assess the side effects of certain medications.
 

How should you prepare for a liver function examination?  

Your physician will provide detailed instructions on preparing for the blood sample aspect of the examination.  

Certain medications and foods may influence the levels of these enzymes and proteins in your bloodstream. Your doctor might ask you to refrain from certain medications or to fast for a period before the examination. However, it's important to continue drinking water before the test.  

Consider wearing a shirt with sleeves that can be easily rolled up to facilitate the medical professional's medical professional's collection of your blood sample.
 

How is a liver function test conducted?

Your blood may be taken at a hospital or a specialised testing centre. To perform the test:

• The healthcare technician will disinfect your skin before the test to minimise the risk of germs on your skin causing an infection.
• They will likely place an elastic band around your arm to make your veins more prominent. They will then use a needle to extract blood samples from your arm.
• Once the blood is drawn, the technician will cover the puncture site with gauze and a bandage. Your blood sample will then be sent off for laboratory analysis.
   

Potential risks associated with a liver function test

Blood draws are standard procedures and are seldom linked to serious complications. Nonetheless, the risks of having a blood sample taken can include:

• bruising under the skin, or hematoma
• excessive bleeding
• feeling faint
• infection
   

What are the subsequent steps after a liver function test?

Following the test, you can typically return to your normal activities. However, if you experience dizziness or lightheadedness during the blood draw, it's advisable to rest before leaving the testing facility.

• The results from these tests might not pinpoint your exact condition or the extent of liver damage, but they can assist your doctor in deciding on the next course of action. Your doctor will call you with the results or review them in a follow-up visit.
• Generally, if your results indicate liver function issues, your doctor will examine your medications and previous medical history to help ascertain the underlying cause.
• If you consume alcohol regularly, you will need to refrain from drinking it. If your doctor determines that a particular medication is causing the raised liver enzymes, they will recommend discontinuing that medication.
   

Additional diagnostic tests

Your doctor may opt to test you for hepatitis, other infections, or additional conditions that could impact the liver. They might also conduct imaging tests like ultrasound or CT scans.

Moreover, they may suggest a liver biopsy to assess the liver for fibrosis, fatty liver disease, or other liver-related issues.
 

Summary

At TruePal, we understand your health, which is why liver function tests are a crucial part of our comprehensive health checkups. These blood tests help evaluate liver health, and variations in specific protein or enzyme levels can alert doctors to potential issues such as liver cancer, fatty liver disease, or hepatitis. Liver function tests can also reveal if certain medications are harming your liver or help monitor the progression of liver disease. After undergoing a liver function test, your doctor will help you understand the results and discuss their significance. If liver disease is suspected, you may need additional tests, such as imaging or a liver biopsy. For a thorough health checkup, explore TruePal’s health checkup services here.
 

FAQs

1. Is it necessary to fast before taking the LFT test? 

The LFT test does not need fasting. You can eat and drink as usual before the test.

2. How can I determine if my liver is functioning correctly?  

A set of liver function tests can reveal indications of liver disease, the severity of the disease, and liver failure. These tests assess liver products such as enzymes, proteins, and bilirubin levels in your bloodstream. Blood tests may also show signs of inflammation, specific illnesses, or side effects like impaired blood clotting.

3. Can liver function tests identify fatty liver?  

Elevated results from liver function tests (LFTs) are frequently the primary reason patients with metabolic-associated fatty liver disease (MAFLD) are referred to specialist care.

4. How long does it take to conduct liver function tests?  

The test should take no more than 5 minutes, followed by a 30-minute wait for the results.

5. What is the normal range for bilirubin levels?  

Generally, healthy bilirubin levels are below 1 milligram per deciliter (mg/dL). Adults experiencing jaundice have bilirubin levels exceeding 2.5 mg/dL. In otherwise healthy newborns, bilirubin levels above 15 mg/dL may lead to complications.

6. Is an ALT level of 70 considered high?  

Among ALT tests conducted in general practice, 68.7% showed normal ALT levels (0–30 IU/l), 21.1% showed levels between 30–50 IU/l, 5.6% had levels between 50–70 IU/l, 2.6% ranged from 70–100 IU/l, and 2% were at 100 IU/l or higher. The occurrence of elevated ALT levels was roughly twice as high in males compared to females across all levels of elevation.