A liver function test (LFT), also called a hepatic function panel, is a blood test that measures the levels of enzymes and proteins excreted by your liver.
While some of these tests measure how well the liver performs its normal functions, others measure enzymes that liver cells release during liver damage or disease.
LFTs help diagnose and monitor liver disease or damage. If the levels are higher or lower than the normal range, it indicates that a person’s liver is not functioning optimally.
When is a liver function test done?
A physician requests an liver function test to establish the presence of damage or inflammation in the liver. LFTs help to:
- Screen for infection or inflammation affecting your liver, such as hepatitis (infectious or alcoholic)
- Aid in the diagnosis of other conditions such as gallstones
- Assess progression and severity of liver disease and determine response to therapy
- Monitor adverse effects if you are taking prescription or non-prescription medicines that can affect liver functioning
- Weakness or fatigue
- Loss of appetite
- Abdominal pain or swelling
- Passing dark-coloured urine or light-coloured stool
- Having a family history of liver diseases
- Being overweight while having diabetes or hypertension
How do I prepare for an liver function test?
Having an LFT done doesn’t require any special preparation. The technician can collect the sample at any time of the day. Some medicines may affect the test outcomes, so it may be helpful to let your physician know about all prescription and non-prescription drugs you take.
How is a liver function test performed?
Your blood will be drawn in a hospital or a diagnostic centre. To administer the test:
- A nurse or a para-medical staff will first clean your skin before the test at the injection site to minimise the possibility of infection due to any microorganisms on the skin
- An elastic strap is wrapped on the arm, which will help in making your veins visible. Then, a needle is used to draw blood samples from your arm.
- Some gauze and a bandage is placed over the puncture site after drawing the blood. Then, the blood sample is sent to a laboratory for testing.
What tests does an Liver Function Test include?
An LFT cannot provide a diagnosis independently but can provide important clues about potential liver function problems.
Here are the standard tests included in an liver function test panel:
- Alanine transaminase (ALT): ALT is an enzyme found in liver cells that helps convert proteins into energy. The normal range is from7 to 55 units per litre (U/L). During liver infection, inflammation, or any other form of damage, hepatic cells release increased quantities of ALT into the bloodstream.
- Aspartate transaminase (AST): The enzyme AST helps metabolize amino acids. Like ALT, AST usually is present in blood at low levels. Average values range from 8 to 48 U/L. When liver damage sets in, AST levels rise in the blood.
- Alkaline phosphatase (ALP): ALP is an enzyme in the liver and bone and plays a crucial role in breaking down proteins. ALP levels typically range from 40 to 129 U/L. Levels of ALP beyond this range may indicate liver damage or diseases, such as a blocked bile duct or certain bone diseases.
- Albumin and total protein: Proteins are vital in the body for a host of functions, including immunity. Albumin is one such protein. Albumin levels in the blood usually range from 3.5 to 5.0 grams per deciliter (g/dL), and total proteins from 6.3 to 7.9 g/dL. When albumin levels and total protein are lower than normal, it may indicate liver damage or disease.
- Bilirubin: Bilirubin is a compound produced during the physiological breakdown of red blood cells. Bilirubin levels in the blood usually range from 0.1 to 1.2 mg/dL. Elevated bilirubin levels (jaundice) may indicate liver damage or disease or certain types of anemia.
- Gamma-glutamyltransferase (GGT): GGT is a liver enzyme. In blood, its levels generally range between 8 to 61 U/L. The presence of GGT levels beyond this range may indicate liver or bile duct damage.
- L-lactate dehydrogenase (LDH): LDH is an enzyme found in the liver. Elevated levels may indicate liver damage. However, its levels can be high in other clinical conditions as well.The normal range for LDH levels in the blood is 122 to 222 U/L.
- Prothrombin time (PT): PT measures the time it takes for your blood to clot and ranges from 9.4 to 12.5 seconds. When PT is higher than this normal range, it may indicate liver damage, but its levels can also increase if you’re taking anticoagulants (blood-thinning drugs), such as warfarin.
The results mentioned here vary from laboratory to laboratory and might be slightly different for women and children.
When to Avoid Liver Funtion Test?
There is no specific condition when this test should be avoided. Inform your doctor about any medications, prescription or over-the-counter medications, including herbal supplements, that may affect the liver function test results.
What are the common conditions which cause abnormal LFTs?
Some common causes which can result in high values for liver function tests are:
Fatty liver disease
Fatty liver disease develops when fat builds up in the liver. If this build-up is due to long-term alcohol consumption, it is known as alcoholic fatty liver disease.
When alcohol is not a causative factor for fat accumulation in the liver, the condition is called non-alcoholic fatty liver disease (NAFLD). People who have metabolic syndrome are at a higher risk of NAFLD.
Although fatty liver may primarily be asymptomatic, it may cause tiredness and pain on the right side of the abdomen.
Metabolic syndrome encompasses a group of symptoms that enhance cardiovascular risk. These symptoms include:
- High blood sugar
- High blood pressure
The physician may get an LFT done for individuals with two or more of these symptoms.
Hepatitis means inflammation of the liver. There are several different strains of hepatitis-causing viruses, which are called A, B, C, D, and E. The symptoms resulting from infection by all these strains are similar.
Common hepatitis symptoms include:
- Yellowing of the eyes and skin (jaundice)
- Loss of appetite
- Abdominal pain
- Muscle soreness
- Joint pain
- Dark urine
A physician may test a person with symptoms of hepatitis to check for elevated liver enzymes.
Alcohol or drug use disorder
Inflammation of the liver can occur due to drinking too much alcohol (alcoholic hepatitis) or indulging in substance abuse (toxic hepatitis). All forms of hepatitis have similar symptoms. In a history of alcoholism or substance abuse, the physician may get an liver function test done to check for disease onset and progression and monitor treatment.
Untreated hepatitis or fatty liver disease has a high risk of progressing to cirrhosis. Patients with cirrhosis experience fatigue, itching, and other symptoms common to hepatitis and fatty liver disease.
A physician may check liver enzyme levels to assess progression and monitor response to therapeutic interventions.
Less common conditions that can cause elevated liver enzymes:
- Autoimmune hepatitis
- Liver cancer
- Celiac disease
- Hemochromatosis (when the body absorbs high levels of iron)
- Wilson’s disease (caused by excessively high levels of copper accumulating in the liver)
- Polymyositis (inflammation of muscles)
- Certain medications, including analgesics, anti-inflammatories, and statins
What is the treatment approach for elevated liver enzymes?
Therapeutic intervention for elevated liver enzymes will focus on managing the underlying condition causing the increased levels.
Fatty liver disease
For NAFLD, individuals can work with their physician to make lifestyle changes such as:
- Exercising more
- Eating a healthy, balanced diet
- Leading an active lifestyle, including reducing stress and improving sleep hygiene
If a person has alcoholic fatty liver disease, the doctor will provide guidance, education, and support about decreasing alcohol intake in any form.
The treatment strategy for metabolic syndrome is similar to fatty liver disease:
- Exercising more and losing weight
- Eating a healthful, balanced diet
- Managing blood sugar levels
- Reducing stress levels (meditation, mindfulness, yoga, journaling)
Also Read: How Many Calories Should I Eat A Day
A physician will recommend the following strategies for acute hepatitis:
- Bed rest
- Plenty of fluids
- Dietary modification
- Avoiding alcohol
Treatment for long-term ineffective hepatitis usually includes an antiviral medication regimen.
Alcoholism or drug abuse or drug misuse
Treatments for chronic alcoholism or drug use disorder include:
- Behavioral therapy, including counseling
- Support groups
Cirrhosis is permanent liver damage, so it is not always treatable. However, the underlying cause of liver dysfunction is usually responsive to treatment.
Prompt diagnosis and treatment of infectious, inflammatory, and chronic metabolic conditions that affect the liver can help prevent progression to cirrhosis.
Interventions such as a modified diet, exercise and weight loss, and reduced alcohol consumption can reduce the risk of progressive liver damage and dysfunction.
Abnormal liver function tests: Outlook and Key Takeaways
- Elevated liver enzymes indicate that a person has an inflamed or damaged liver. Many underlying conditions may trigger the onset and progression of liver inflammation or damage.
- Physicians recommend that anyone with symptoms of conditions that raise liver enzyme levels go for an LFT.
If an LFT is abnormal, the physician will investigate potential underlying causes, consolidate a diagnosis and recommend a suitable personalized treatment plan.