Liver Function Tests: What the Panel Includes and How to Read the Results

You have been handed a form where numbers and arrows sit next to ALT, AST, and GGT, with a lab note saying "normal" below. Not everyone can immediately grasp what exactly was tested and how serious things are. Let's go through it calmly, without panic.

What liver function tests are

Liver function tests are not a single test but a group of blood tests; labs also call this a liver panel or profile. The blood sample is used to measure several substances that the liver synthesizes or removes from the body. Some markers show how the organ is working, while others show that disease or injury may have damaged it.

Let me emphasize: liver function tests almost never establish a diagnosis on their own. They are an indicator on the dashboard — they show that something is wrong but do not explain the cause, so abnormal results require further evaluation.

Which markers are included in a liver blood test

The classic set is as follows. Albumin — a protein produced by the liver. Total protein — the sum of albumin and globulins, which are mainly of liver origin. The enzymes ALT, AST, alkaline phosphatase, and GGT. Bilirubin — a breakdown product of old red blood cells that the liver removes from the body. Lactate dehydrogenase, an enzyme found in particularly high amounts in the liver. Prothrombin time — the speed of blood clotting, since prothrombin is also made in the liver.

The form may list everything or only part of it: liver markers are often included in a comprehensive metabolic panel ordered during a preventive checkup.

Why the test is ordered and who needs it

There are several reasons: to find out whether liver disease is causing symptoms; to assess the severity of an already known condition; to monitor the course of the disease and the effect of treatment; to check whether medications being taken are harming the liver.

Symptoms that may prompt a doctor to order such a test include nausea and vomiting, loss of appetite, persistent fatigue and weakness, jaundice — yellowing of the skin and whites of the eyes, abdominal pain and bloating, swelling of the ankles and legs, dark urine and pale stools, and frequent skin itching.

Sometimes there are no symptoms, but the risk is high: a family history of liver disease, alcohol use disorder, obesity, diabetes, use of medications that can damage the liver, and past or current hepatitis.

The tricky part is that most liver diseases cause no symptoms in the early stages: symptoms appear once the organ is already damaged and covered with scars. This is cirrhosis.

How to prepare and how blood is drawn

You are usually asked not to eat or drink for 10–12 hours before the blood draw; your doctor will tell you exactly what applies in your case. Tell them about all medications you take: some affect the results. You must not stop taking them on your own.

The procedure is simple: blood is drawn from a vein in your arm with a thin needle, and it takes less than five minutes. You may feel a slight prick, and sometimes there is minor soreness or a bruise at the puncture site — usually it resolves quickly.

What elevated and decreased markers mean, including GGT

Reading the form based on a single number is pointless: the doctor compares the markers with each other and looks for characteristic combinations. The pattern helps understand what is happening:

• the liver is inflamed — this is hepatitis;
• the hepatitis is related to alcohol or infection;
• the liver is functioning poorly and to what extent;
• there is a problem with the bile ducts;
• the liver is being damaged by medications.

The most commonly encountered reference ranges are: ALT — about 7–41 IU/L, AST — 10–38 IU/L, total bilirubin — 8.5–20.55 µmol/L, albumin — 35–50 g/L. GGT in men — 15–106 µmol/L, in women — 10–66 µmol/L. Reference intervals vary between labs, so you should look at the norms on your own form.

An increase in bilirubin above 27 µmol/L already produces visible jaundice. And a high alkaline phosphatase level is not always about the liver: it can be a sign of bone disease. An abnormality does not equal liver disease at all, and if you have recently been ill, the changes may be temporary — in that case the test is repeated later.

When results require a doctor's consultation

Any abnormality on the form is a reason to see a doctor, not to look for explanations online. The doctor will compare the numbers with your symptoms, history, and medications and, if necessary, order further tests. You should also see a doctor when the markers are normal but you have symptoms: persistent fatigue and weakness, loss of appetite and weight, jaundice, skin itching, nausea and vomiting, abdominal pain or marked bloating, and swelling of the legs and abdomen.

Abnormal liver function tests alone are not a reason to call an ambulance. 103 or 112 — for a life-threatening condition, such as signs of a stroke or heart attack.

This material is for reference: it helps you understand the form but does not replace a doctor's consultation — conclusions are made by a specialist.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer