LFT Normal Range Explained: How to Read Your Liver Function Test Report

A truly healthy ALT (SGPT) is lower than most Indian lab reports suggest. The ACG 2017 guideline puts the healthy upper limit at 29–33 IU/L for men and 19–25 IU/L for women; a South Indian study found 28 and 24 IU/L. A report that prints “normal up to 40 or 50” can hide early fatty liver. Use your lab’s range, but ask your doctor about anything above 30.
— Dr Chetan Kalal, DM Hepatology, Gleneagles Hospital Mumbai

A composite of a patient I meet most weeks: a 38-year-old software engineer from Powai brings a corporate health-check report. SGPT 58, SGOT 34, everything else “within normal limits”. Told: slightly raised, repeat in six months. Six months later it is 71. No symptoms, no alcohol, not visibly overweight. Ultrasound shows fatty liver. He is here because a friend told him not to wait for a third report.

That report, and the way it was read, is the subject of this article. The liver function test (LFT) is the commonest liver investigation in India and the most commonly misread. The numbers are not difficult. What takes experience is knowing which ones matter, how they move together, and what they cannot tell you. I will take each in turn. One rule first: the reference interval printed beside each value belongs to that laboratory and its method. Use it. Figures below are typical, not universal.

What does each test in an LFT measure?

“Liver function test” is a misnomer that has stuck. Most of the panel measures injury, not function — the ACG guideline of 2017 prefers “liver chemistries” for this reason. Three groups:

Enzymes that leak out when liver cells are injured. ALT (alanine aminotransferase, SGPT) and AST (aspartate aminotransferase, SGOT) sit inside liver cells and spill into the blood when cells are inflamed or dying. ALT is the more liver-specific; AST is also found in muscle, heart and red cells.

Enzymes that rise when bile flow is blocked. ALP (alkaline phosphatase) and GGT (gamma-glutamyl transferase) line the bile ducts and rise when bile cannot drain — a stone, a stricture, certain drugs. ALP also comes from bone; GGT is the tie-breaker: raised ALP with raised GGT points to the liver.

Tests that genuinely measure function. Bilirubin is the yellow pigment from worn-out red cells; the liver must process it (the “direct” fraction) and excrete it in bile. Albumin is the main protein the liver manufactures; total protein adds the globulins made elsewhere. PT/INR measures clotting factors the liver produces. Falling albumin with a rising INR means the liver’s manufacturing capacity is failing — the thing we watch in cirrhosis.

What is a normal SGPT (ALT) level?

Lower than you have been told. The upper limits printed on most reports were set decades ago using “healthy” populations that quietly included people with undiagnosed fatty liver and hepatitis C. A study of 6,835 first-time blood donors in Milan, published in the Annals of Internal Medicine in 2002, recalculated the limits using only people at lowest risk of liver disease and arrived at 30 U/L for men and 19 U/L for women. The old limits picked up 55% of donors with hepatitis C viraemia; the new ones, 76%.

The ACG guideline of 2017 states a true healthy ALT ranges from 29 to 33 IU/L for men and 19 to 25 IU/L for women, with anything above this needing assessment. An ALT of 38 in a woman is not “within normal limits” by any modern standard, whatever the report says.

Indian data agree. A study from JIPMER, Puducherry, screened 2,600 adults and kept the 344 who were genuinely healthy — normal BMI, no fatty liver, no alcohol, no medicines, negative hepatitis serology. Their 97.5th-percentile ALT was 28 IU/L in men and 24 IU/L in women. A Mumbai study of 4,917 blood donors found mean ALT of 27 IU/L in men and 17.7 IU/L in women, rising steadily with BMI and waist-to-hip ratio. Our population needs a lower threshold, not a higher one.

So the number to remember is 30. Below it, inflammation is unlikely. Above it, the commonest explanation in Mumbai today is fatty liver, then hepatitis B, hepatitis C, alcohol and medicines. Above three times the upper limit, I want to see you within the week, not in six months.

Hepatocellular, cholestatic, or just bilirubin: what the pattern tells us

Doctors do not read an LFT value by value. We read the shape. The ACG guideline defines two patterns; a third situation sits apart.

Hepatocellular pattern. ALT and AST are raised out of proportion to ALP: the liver cells themselves are inflamed. Usual suspects are fatty liver, viral hepatitis, alcohol, drugs and herbs, and autoimmune hepatitis. The guideline’s work-up covers hepatitis A, B and C, fatty liver and alcohol assessment, iron studies, autoimmune markers and — in younger patients — Wilson’s disease.

Cholestatic pattern. ALP is raised out of proportion to ALT and AST, usually with GGT keeping it company: bile flow is the problem. Ultrasound comes first, looking for dilated ducts, stones or a mass. If the ducts are normal, the guideline directs testing for primary biliary cholangitis and primary sclerosing cholangitis.

Isolated raised bilirubin. When total bilirubin is mildly raised, the direct fraction is normal and every enzyme is normal, the overwhelmingly likely explanation is Gilbert’s syndrome — an inherited, harmless variation in the enzyme that conjugates bilirubin. It climbs with fasting, illness and stress, and needs no treatment once confirmed. The guideline’s instruction is simple: fractionate the bilirubin. A raised direct bilirubin is a different matter, and implies liver-cell disease or obstruction until proven otherwise.

What does the SGOT:SGPT (AST:ALT) ratio mean?

In most liver inflammation ALT runs higher than AST, so the ratio sits below 1. When it flips, that means something.

The best-known use is in alcohol. A Swedish study in Alcohol and Alcoholism compared 313 alcohol-dependent patients admitted for withdrawal, 78 admitted for other medical reasons, and 48 admitted with alcohol-related cirrhosis. Among the withdrawal group — heavy drinkers without severe liver disease — 64% had a ratio of 1 or less, and a ratio of 2 or more was exceptional. In the cirrhosis group, 69% had a ratio of 2 or more. In the authors’ words, a high AST/ALT ratio “suggests advanced alcoholic liver disease” rather than merely heavy drinking. The ratio is a marker of damage, not of consumption.

The second use is in scarring from any cause. As fibrosis advances, ALT tends to fall and AST tends to hold or rise, so the ratio drifts above 1 even in fatty liver or hepatitis C — which is why AST sits in the FIB-4 score, and why I look twice at a “mild” elevation where AST has overtaken ALT. If you drink and your SGOT exceeds your SGPT, read my article on alcohol-related liver disease and come in.

Can my LFT be normal and my liver still be damaged?

Yes, and this is the single most important thing on this page. The LFT measures inflammation at the moment of the blood draw. Cirrhosis is the result of years of inflammation that may have burnt out. A scarred liver can be quiet.

The clearest proof is a 2003 study in Hepatology. Researchers compared 51 people with fatty liver on biopsy and entirely normal ALT with 50 whose ALT was raised. Histology was the same across the two groups. Among the 51 with normal ALT, 12 had bridging fibrosis and 6 already had cirrhosis; diabetes was the one factor that independently predicted advanced disease. In the authors’ words, the entire histologic spectrum of fatty liver disease “can be seen in individuals with normal ALT values”.

So a normal LFT answers one question — is my liver inflamed today? — and not the one people actually want answered, which is whether it is scarred. For that we use a FIB-4 score (from age, AST, ALT and platelet count) and then FibroScan, a ten-minute painless scan of liver stiffness. Where results conflict, a liver biopsy settles it. The British Society of Gastroenterology’s 2018 guideline says the same: pattern and context, not the size of the abnormality, should decide further investigation. Anyone with diabetes, obesity, fat on ultrasound (whatever the grade), long-standing hepatitis B or heavy alcohol use deserves a fibrosis assessment however clean the LFT looks.

When should an abnormal LFT send you to a hepatologist?

Most mild abnormalities are fatty liver, and the first step — weight loss, no alcohol, a repeat test in a few weeks — can be started by your family physician. Some findings should not wait. See a liver specialist promptly, not in six months, if any of these apply:

• ALT or AST more than three times the upper limit, or any value still rising on repeat.
• A raised direct bilirubin, or visible jaundice (yellow eyes, dark urine, pale stools).
• Low albumin, raised INR or low platelets alongside abnormal enzymes — a liver failing to do its job.
• Abnormal LFTs with abdominal or leg swelling, confusion, drowsiness or vomiting of blood. These are emergencies.
• Abnormal enzymes within weeks of starting a new medicine, tuberculosis treatment, bodybuilding supplement, or herbal or ayurvedic preparation.

Now the thing not to do. Many patients respond to a raised SGPT by starting a “liver tonic” from the chemist or a herbal preparation a relative recommended. Please do not. Nothing over the counter repairs a liver, and some of these products injure it. During the COVID-19 pandemic I co-authored a nationwide Indian study documenting liver injury from Giloy (Tinospora cordifolia), taken by many as an immunity booster. Herbal and ayurvedic preparations now sit among the leading causes of drug-induced liver injury in India. If your LFT is abnormal, find out why — and the first question your doctor should ask is what you are already taking.

For the engineer in that composite, the path was short: a FIB-4 that was not low, a FibroScan showing early fibrosis at 38, and a weight-loss plan instead of a tonic. His ALT was 24 a year later. The report had been telling the truth all along. It just needed to be read.

References

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