What a liver function test means

A liver function test is not one test. It is a panel of five or six separate measurements that answer two different questions, and reading it well means keeping those questions apart.

The first is: are liver cells under stress? That is what the enzymes tell you. SGPT (also written ALT) sits mostly inside liver cells and leaks out when they are irritated or damaged, which makes it the most liver-specific number on the sheet. SGOT (AST) does the same but is also present in muscle and heart, so it is less specific on its own — its value lies in the ratio to SGPT.

The second question is: how well is the liver working? That is what bilirubin and albumin tell you. Bilirubin is the pigment the liver clears from broken-down red cells; albumin is a protein the liver manufactures. These move late, and they move in genuinely impaired function rather than in irritation.

Alkaline phosphatase sits slightly apart. It rises when bile flow is obstructed, and also comes from bone, which is why it is usually interpreted alongside GGT.

The panel is therefore better described as a liver panel than a liver function test. Most abnormal LFTs in practice are abnormal enzymes with entirely normal function.

Start by reading against the range printed on your own report, not one you have found elsewhere. Reference ranges vary by laboratory method, and some labs use noticeably lower upper limits than others.

Then look at the pattern rather than the worst number.

A mildly raised SGPT and SGOT with normal bilirubin and albumin is by far the commonest picture. In the Indian population it most often reflects metabolic fatty liver. It is a finding to investigate over the next few months, not over the next few days.

A raised SGOT relative to SGPT, with a ratio above two, shifts attention towards alcohol as a contributor.

A raised ALP with a raised GGT points to the bile ducts rather than the liver cells, and usually leads to an ultrasound.

A raised bilirubin in isolation, with entirely normal enzymes, is frequently Gilbert's syndrome — an inherited variation in bilirubin processing that affects a few percent of people, causes no harm, and typically becomes more obvious during fasting or illness.

A low albumin, or a rising bilirubin with a prolonged prothrombin time, is a different category. These suggest function is affected, and they need proper assessment rather than reassurance.

Enzyme values in the thousands usually indicate acute injury — a viral hepatitis, a drug reaction, or an ischaemic event — and are managed urgently.

If your enzymes are mildly raised and the rest of the panel is normal, three things are worth doing.

Look for the cause rather than only repeating the number. In practice that means an abdominal ultrasound, an HbA1c and a fasting lipid profile, hepatitis B and C serology, and an honest account of alcohol intake and of every supplement and over-the-counter medicine being taken. Bodybuilding supplements and some herbal preparations are a recognised and frequently missed cause.

Repeat the panel after eight to twelve weeks, not after one. Enzymes fluctuate, and a value drawn two days after unaccustomed exercise or a viral illness can mislead. What you are looking for is a trend.

Ask whether fibrosis has been assessed. A FIB-4 score can be calculated from tests you have probably already had, and it is the calculation that separates a finding to act on calmly from one that needs specialist input.

Stop alcohol while this is being sorted out, and do not start a liver supplement. There is no evidence that any of them lower enzymes, and several have been reported to raise them.

ⓘThis information is educational and not a diagnosis.