Liver function tests Your guide to knowing if they detect viruses or not

The liver is one of the most important organs in the body, as it performs vital functions such as detoxifying the blood and producing essential proteins. When any dysfunction occurs, serious health problems can appear. That’s why liver function tests have become one of the basic examinations for early detection of liver issues.However, a common question many people ask is: Do liver function tests detect viruses like hepatitis B or C?
In this Dalily Medical article, we’ll explain the role of liver function tests, what they actually detect, which tests confirm the presence of viral hepatitis, and everything you need to know to protect your liver and understand your test results correctly.

What Are Liver Function Tests?

Liver function tests (LFTs) are a group of blood tests that measure levels of enzymes and proteins in the blood to evaluate how well the liver is working. Their main purpose is to determine whether the liver is functioning properly or if there is any damage or underlying problem.

Key components of the test include:

ALT (Alanine Aminotransferase): High levels indicate damage to liver cells.
AST (Aspartate Aminotransferase): Helps detect problems in the liver or muscles.
Bilirubin: Measures the yellow pigment produced from the breakdown of red blood cells; high levels can cause yellowing of the skin or eyes (jaundice).
Albumin: A protein made by the liver; low levels suggest poor liver function.

Do Liver Function Tests Detect Cancer?

Liver function tests are not designed to directly detect cancer, but they may give clues to serious liver conditions:

Advanced fatty liver disease or liver cirrhosis may suggest severe liver damage.
Increased protein levels in the blood can sometimes be associated with conditions like lymphoma or leukemia.

When Are Liver Function Tests Ordered?

Doctors usually request LFTs when symptoms suggest a liver problem, such as:

Yellowing of the skin or eyes (jaundice)
Persistent fatigue
Loss of appetite or nausea
Abdominal pain
Changes in urine or stool color

How to Read Liver Function Test Results

1. Test abbreviations and their meanings:

ALT (SGPT): High levels indicate liver cell damage.
AST (SGOT): Elevated levels may be due to liver or heart problems.
ALP: Increased levels suggest bile duct problems.
Bilirubin: High levels indicate bile duct obstruction or liver disease.

2. Normal ranges:

ALT: Less than 40 U/L
AST: Less than 40 U/L
ALP: 44–147 U/L
Total Bilirubin: Less than 1.2 mg/dL

Is Fasting Required?

Yes, in most cases fasting for 8–12 hours is recommended to get accurate results.
Drinking water is allowed during fasting.

What Do Liver Function Tests Detect?

Liver cirrhosis: Helps with early detection of liver damage.
Viral hepatitis: Such as hepatitis B or C (suggested, not confirmed).
Fatty liver disease: Elevated enzymes may indicate it.
Bile duct disorders: Such as bile duct obstruction.
Other conditions: Including cancer or liver-related diseases.

Frequently Asked Questions

1️⃣ Do liver function tests detect viruses?
Yes, LFTs can indicate liver problems caused by viruses like hepatitis B or C if enzyme or protein levels are abnormal.
However, specific viral tests are needed to confirm infection.

2️⃣ Can liver cancer be detected through liver function tests?
No, LFTs do not directly detect cancer. Extremely high values may signal the need for further tests such as imaging or advanced blood tests.

3️⃣ How long does it take to get results?
Results usually appear within 24–48 hours, depending on the lab.

4️⃣ Can the test be repeated regularly?
Yes, some conditions require regular monitoring to track disease progression or treatment response.

5️⃣ Can children take this test?
Yes, it’s safe for children. A smaller blood sample is taken, and labs handle pediatric cases carefully.

6️⃣ Does pregnancy affect results?
Some enzyme and protein levels may change during pregnancy, so the doctor should know before interpreting results.

7️⃣ Does the test detect fatty liver?
LFTs may show elevated enzymes related to fatty liver, but they do not confirm it. Ultrasound or additional tests are needed.

8️⃣ Do food and drinks affect results?
Yes. Fatty foods, sugar, and alcohol before the test can temporarily raise enzyme levels, which is why fasting is important.

9️⃣ How often should chronic liver patients test?
It depends on the condition, but many patients repeat the test every 3–6 months.

❓ Does high enzyme levels always mean a serious disease?
No. Sometimes elevations are temporary due to medications, fatigue, or certain foods. The doctor determines the cause and follow-up.

❓ Can results be inaccurate?
Yes, results can be affected by:

Not fasting before the test
Certain medications or supplements
Intense exercise before testing

In such cases, the doctor may ask to repeat the test.

Types of Liver Function Tests

1️⃣ Liver Enzyme Tests

Measure enzymes that rise when liver cells are damaged:

ALT (Alanine Aminotransferase): Often indicates liver damage.
AST (Aspartate Aminotransferase): May come from liver, heart, or muscles.
ALP (Alkaline Phosphatase): Linked to bile ducts or bone disorders.
GGT (Gamma-glutamyl transferase): Often elevated in liver or gallbladder disease or alcohol use.

2️⃣ Liver Protein Tests

Total Protein: Reflects the liver’s ability to produce proteins.
Albumin: Low levels indicate poor liver function or malnutrition.

3️⃣ Blood Clotting Tests

PT (Prothrombin Time): Measures how fast blood clots; prolonged time suggests liver problems.

4️⃣ Bilirubin Tests

Total, Direct, and Indirect Bilirubin: High levels cause jaundice and indicate liver or bile duct disorders.

5️⃣ Additional Tests Depending on the Case

LDH (Lactate Dehydrogenase): Used to assess liver tissue damage in certain cases.
Alpha-fetoprotein (AFP): Used to monitor some types of liver tumors.

How Is a Liver Function Test Performed?

A liver function test is a simple but very important blood test used to assess liver health. Here are all the steps, from preparation to receiving results:

1️⃣ Preparation Before the Test

Fasting: Most liver function tests require fasting for 8–12 hours before the test. Only water is allowed.
Inform your doctor about medications and supplements: Some medications, such as painkillers or herbal supplements, may affect results.
Avoid alcohol and intense exercise: Alcohol or strenuous exercise before the test can temporarily raise liver enzyme levels.

2️⃣ Blood Sample Collection

Sitting or lying down: To keep the arm relaxed during blood draw.
Disinfection of the puncture site: Usually in the arm, using alcohol or another antiseptic to prevent infection.
Applying a tourniquet: To make the vein more visible.
Inserting the needle into the vein: A small amount of blood is drawn into a tube.
Removing the needle and covering the site: With gauze or a bandage to stop bleeding.

3️⃣ Sample Handling

The tube is placed in a special container to prevent contamination.
The sample is sent to the laboratory, where enzymes, proteins, and bilirubin levels are analyzed.

4️⃣ After Blood Collection

Apply pressure to the puncture site to prevent bruising or bleeding.
Monitor for unusual signs such as severe redness or swelling.
Drink water and eat normally after the test.

5️⃣ Receiving the Results

Results usually appear within 1–2 days, depending on the laboratory.
The doctor interprets the results and determines whether there is a liver problem or a need for additional tests.

Normal Results of Liver Function Tests

Normal values vary depending on gender, body size, and laboratory standards. The table below shows typical reference ranges for adult men (values may differ slightly for women and children):

Test	Normal Range
ALT (Alanine Aminotransferase)	7–55 U/L
AST (Aspartate Aminotransferase)	8–48 U/L
ALP (Alkaline Phosphatase)	40–129 U/L
Albumin	3.5–5 g/dL
Total Protein	6.3–7.9 g/dL
Bilirubin	0.1–1.2 mg/dL
GGT (Gamma-glutamyl Transferase)	8–61 U/L
LDH (Lactate Dehydrogenase)	122–222 U/L
Prothrombin Time (PT)	9.4–12.5 seconds

Note: Reference values may vary slightly by laboratory. Your doctor is the final authority in interpreting results.

What Do Liver Function Test Results Mean?

Liver function tests provide insight into liver health, but abnormal results in a single test may be caused by factors unrelated to liver or bile duct disease.
Conversely, some people with serious liver disease may still have normal results.

Generally, one or more abnormal results indicate the need for further evaluation.

1️⃣ Elevated Liver Enzymes (ALT & AST)

Indicate leakage from liver cells due to inflammation or cell death.
ALT higher than AST often suggests acute liver injury, such as viral hepatitis.
Sometimes elevations come from muscles or the heart; this is checked by measuring Creatine Kinase (CK) or Troponin.
GGT is more sensitive for detecting liver damage related to drugs, alcohol, or obesity.

2️⃣ Elevated Bilirubin

Commonly associated with liver disease or bile flow obstruction (e.g., gallstones).
Causes pale stools and dark urine.
May also occur due to excessive breakdown of red blood cells, such as in newborns or sickle cell anemia.
In these cases, total and conjugated bilirubin are monitored.

3️⃣ Elevated Alkaline Phosphatase (ALP)

Often due to bile duct obstruction or liver disease.
May also be related to bone conditions such as fractures or vitamin D deficiency.
GGT helps differentiate: it rises with ALP in liver disease but stays normal in bone disorders.

4️⃣ Low Albumin

Albumin is produced only by the liver.
Low levels indicate significant loss of liver tissue in chronic disease.
Other causes include malnutrition, kidney disease, protein loss in urine, and inflammatory conditions.

5️⃣ Total Protein

Usually normal in liver disease.
If albumin decreases, globulin levels may increase, especially in alcoholic or autoimmune hepatitis.

6️⃣ Prolonged Prothrombin Time (PT)

Indicates deficiency of clotting factors made by the liver or vitamin K deficiency.
Patients may bruise easily or have delayed wound healing.
Causes include severe malnutrition, chronic alcohol use, or bile duct obstruction.

Possible Risks of Liver Function Tests

1️⃣ Problems at the Blood Draw Site

Bruising or mild swelling: Common and resolves in a few days.
Temporary redness or irritation: Usually mild.
Minor bleeding: Rare; more likely in clotting disorders or if pressure isn’t applied properly.

2️⃣ Dizziness or Fainting

Lightheadedness: Due to fasting or a small blood loss.
Brief fainting: Rare, more common in adolescents or sensitive individuals.

3️⃣ Infection

Extremely rare due to sterile, single-use needles and proper skin disinfection.

4️⃣ Issues in Certain Patients

Patients on blood thinners: Higher risk of bruising or bleeding.
Elderly or those with fragile veins: Increased chance of bruising or swelling.

5️⃣ Very Rare Side Effects

Severe pain at the puncture site: Usually due to needle placement.
Rare allergic reaction: To disinfectants or gloves.

⚠️ Tips to Reduce Risks

Apply pressure to the puncture site for 1–2 minutes after the draw.
Drink water before and after the test to avoid dizziness.
Remain seated or lying down during the procedure.
Inform the healthcare provider about blood thinners or chronic illnesses.

Tips Before and After a Liver Function Test

Before the Test

1️⃣ Fasting:

Fast for 8–12 hours.
Avoid food and sugary or fatty drinks.
Water is allowed.

2️⃣ Avoid certain medications and supplements:

Painkillers (like paracetamol) and anti-inflammatory drugs may affect results.
Some vitamins and herbal supplements can also alter results—consult your doctor.

3️⃣ Avoid alcohol:

Alcohol can temporarily elevate liver enzymes.
Avoid it for at least 48 hours before testing.

4️⃣ Avoid intense exercise:

Strenuous workouts may temporarily raise enzyme levels.

5️⃣ Inform your doctor about your health status:

Mention chronic diseases, special diets, or previous liver conditions.

After the Test

1️⃣ Drink water and eat normally.
2️⃣ Monitor the puncture site:

Minor bruising or redness is common and usually resolves on its own.
3️⃣ Wait for results and consult your doctor:
Results may be available the same day or the next day.
If abnormalities appear, your doctor will determine the cause and recommend further tests or treatment.
4️⃣ Don’t panic over unexpected results:
Minor factors like food or exercise can affect results.
Your doctor is the best person to judge whether there is a real problem.