Liver Function Test (LFT)
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Overview
A Liver Function Test (LFT) is a simple blood test that gives a snapshot of how well your liver is working. It measures several enzymes and proteins produced by the liver, and is one of the most commonly ordered blood tests.
An LFT is part of most routine health check-ups. It is also the first test ordered when liver disease is suspected — and is used to monitor anyone with known liver problems, on certain long-term medications, or with risk factors like
fatty liver, hepatitis, or alcohol use.
What is this test?
An LFT panel typically measures: bilirubin (a waste product the liver clears), AST and ALT (enzymes that rise when liver cells are damaged), ALP and proteins (albumin and total protein) which the liver produces.
Different patterns of abnormality point to different problems — for example, very high ALT suggests liver cell damage, while a high ALP with bilirubin suggests a bile duct problem.
Why your doctor may order it
- Investigation of suspected liver disease
- Persistent fatigue, nausea, or unexplained symptoms
- Jaundice (yellow eyes or skin)
- Suspected hepatitis A, B, C, or other infections
- Suspected fatty liver — particularly with obesity, diabetes, or high cholesterol
- Monitoring known liver disease
- Before starting and during certain long-term medications (including statins, anti-tuberculosis drugs, anti-seizure medications)
- Routine annual health check-up
- Pre-operative assessment
How long does it take?
The blood draw itself takes 2 to 5 minutes. Including registration and waiting, total time at the lab is usually 2-3 hrs.
How to prepare
- Tell us about all medications, supplements, and herbal preparations you take. Many affect liver enzymes.
- Avoid alcohol for at least 24 hours before the test.
- Avoid heavy exercise for 24 hours — strenuous activity can temporarily raise some liver enzymes.
- Bring your prescription, ID, and any previous LFT reports for comparison.
What to expect during the test
A small blood sample is taken from a vein in your arm. The phlebotomist will clean the area, tighten a band above the elbow, and use a small needle. The sample is collected into one. The needle is in for a few seconds. Most people feel a brief sting. You will be given cotton wool to press on the spot and a small adhesive bandage.
After the test
- Resume normal activities immediately. You can eat as soon as you leave the lab.
- A small bruise at the puncture site is occasionally seen — it settles in a few days.
- Reports are typically available the same day, and uploaded to the patient portal.
- Discuss the report with your treating doctor — small variations are common, and the pattern of results matters more than any single number.
Do's and Don'ts
- Tell us about all medications and supplements, including ayurvedic and herbal products.
- Drink plenty of plain water before the test — well-hydrated veins are easier to draw from.
- Bring previous LFT reports for trend comparison.
- Mention any history of liver disease, hepatitis, or significant alcohol use.
- Don't drink alcohol for at least 24 hours before the test.
- Don't do heavy exercise the day before — it can raise muscle enzymes that look similar to liver enzymes.
- Don't panic if a single LFT is mildly abnormal — many normal people have minor variations.
- Don't ignore persistently abnormal LFTs — they need follow-up with a doctor.
Understanding your results
LFT results are reported with normal reference ranges. ALT and AST normal range is typically up to about 40 U/L. ALP up to 130 U/L (higher in growing children and pregnancy). Bilirubin up to 1.2 mg/dL. Albumin 3.5 to 5.5 g/dL. Mild abnormalities are common and often not serious — fatty liver, recent infections, or certain medications can cause them. Significantly raised enzymes, or persistent abnormalities, need investigation. Your doctor will look at the pattern, your symptoms, and your risk factors to decide on the next step
Frequently asked questions
Not necessarily. Mildly raised liver enzymes are common — often due to fatty liver, recent viral infections, alcohol, or certain medications. A persistently abnormal LFT, or a significantly high one, needs proper assessment.
Not really. LFT may be normal even in significant fatty liver. An ultrasound or FibroScan is usually needed to confirm fatty liver. LFT is part of the picture, not the whole picture.
Normal therapeutic doses, occasionally taken, do not significantly affect LFT. High doses or chronic use can — and overdose is a serious cause of liver injury. Tell your doctor about all medications.
It depends. Annual check-ups for healthy adults, 3 to 6 monthly for known fatty liver, more frequently if you are on hepatotoxic drugs. Your doctor will recommend the right interval.
Yes — some can cause significant liver injury. Tell your doctor about everything you take, including supplements that are sold as 'natural' or 'safe'.