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“Learn everything about Liver Function Test (LFT) – purpose, procedure, parameters, normal values, interpretation, and how to monitor liver health effectively. A complete guide for patients and health enthusiasts.”
Liver Function Test (LFT): Complete Guide – Definition, Purpose, Process, Normal Values, and Interpretation
What is a Liver Function Test (LFT)?
A Liver Function Test (LFT) is a set of blood tests that provide detailed information about the health and performance of the liver. The liver is responsible for more than 500 essential functions, including digestion, detoxification, protein synthesis, energy storage, and blood clotting regulation.
LFT measures the levels of specific enzymes, proteins, and bilirubin in the blood to detect:
Liver inflammation
Liver cell damage
Bile duct obstruction
Liver infections (e.g., Hepatitis)
Side effects of medications
Alcohol-related liver injury
❓ Why is LFT Important?
The liver is a vital organ, and early damage often shows no symptoms. That’s why doctors recommend LFT when liver-related problems are suspected.
Common reasons for LFT:
Jaundice (yellow skin and eyes)
Suspected Hepatitis (A, B, C, etc.)
Cirrhosis (scarring of liver tissue)
Fatty liver disease (alcoholic or non-alcoholic)
Long-term alcohol use
Drug-induced liver injury (TB drugs, antibiotics, steroids, chemotherapy)
Gallbladder or bile duct disease
Routine monitoring in chronic diseases (diabetes, obesity, hypertension)
🔍 Parameters Measured in LFT
1. Alanine Aminotransferase (ALT/SGPT)
Normal range: 7 – 55 U/L
High levels indicate liver inflammation or cell injury.
2. Aspartate Aminotransferase (AST/SGOT)
Normal range: 8 – 48 U/L
Elevated in liver disease but also in heart or muscle damage.
3. Alkaline Phosphatase (ALP)
Normal range: 40 – 129 U/L
Raised in bile duct obstruction, gallstones, or bone disease.
4. Gamma-glutamyl Transferase (GGT)
Normal range: 9 – 48 U/L
Sensitive to alcohol-related or drug-induced liver damage.
5. Total Bilirubin
Normal range: 0.1 – 1.2 mg/dL
Elevated levels cause jaundice and indicate impaired bilirubin metabolism.
6. Direct (Conjugated) Bilirubin
Normal range: 0 – 0.3 mg/dL
High levels suggest bile duct blockage or impaired bile excretion.
7. Albumin
Normal range: 3.5 – 5.0 g/dL
Low albumin indicates chronic liver disease or poor nutrition.
8. Total Protein
Normal range: 6.0 – 8.3 g/dL
Reflects liver’s protein production and overall nutritional status.
9. Prothrombin Time (PT/INR)
Normal range: 11 – 13.5 seconds
Prolonged PT suggests impaired liver synthesis of clotting factors.
🩺 How is the LFT Test Done?
Blood is collected from a vein in the arm.
Usually, no preparation is required, but sometimes fasting for 8–12 hours may be recommended.
Results are typically available within a few hours to a day.
The procedure is safe with no major side effects.
⚠️ Symptoms That Require LFT
Yellowing of skin and eyes (jaundice)
Dark urine and pale stools
Persistent fatigue and weakness
Loss of appetite, nausea, or vomiting
Abdominal pain or swelling
Itchy skin without reason
Long-term alcohol or medication use
📊 Normal Range of LFT Values
Parameter Normal Range
ALT (SGPT) 7 – 55 U/L
AST (SGOT) 8 – 48 U/L
ALP 40 – 129 U/L
GGT 9 – 48 U/L
Total Bilirubin 0.1 – 1.2 mg/dL
Direct Bilirubin 0 – 0.3 mg/dL
Albumin 3.5 – 5.0 g/dL
Total Protein 6.0 – 8.3 g/dL
Prothrombin Time 11 – 13.5 seconds
🧾 How to Interpret LFT Results
High ALT & AST: Suggests hepatitis, fatty liver, or drug-induced damage.
High ALP & GGT: Indicates bile duct blockage or alcohol damage.
High Bilirubin: Points to jaundice due to liver or bile duct disease.
Low Albumin: Suggests chronic liver damage or malnutrition.
Prolonged PT: Indicates advanced liver disease or clotting factor deficiency.
🛡️ How to Keep Your Liver Healthy
Limit alcohol consumption
Avoid unnecessary or excessive medications
Maintain a healthy weight
Eat a balanced diet rich in vegetables, fruits, and lean protein
Stay hydrated
Exercise regularly
Get vaccinated against Hepatitis A & B
Go for regular health check-ups if you have diabetes, obesity, or high cholesterol
📝 Conclusion
The Liver Function Test (LFT) is a simple yet powerful diagnostic tool to evaluate liver health. It detects early signs of liver problems, monitors chronic conditions, and guides treatment decisions. Regular LFT check-ups are crucial, especially for people at higher risk of liver disease.
