Liver function test results explained, one marker at a time

A liver panel can look like alphabet soup: ALT, AST, ALP, GGT, bilirubin, albumin. This guide has liver function test results explained in plain words, one marker at a time, so you know what each number tracks and what to ask next. It's general information, not a diagnosis. Your doctor reads your results alongside your symptoms and history.

First, a few things that make the page less scary

The name is a bit misleading. Most of these markers show whether liver cells or bile ducts are under stress, not how well the liver is working. That's why liver charities now prefer the term "liver blood tests". Many people with an abnormal result have a liver that works normally.

Abnormal results are common. Each reference range is set so that about 19 in 20 healthy people fall inside it. That means about 1 in 20 healthy people land just outside it on any one test. Liver UK notes that in almost a third of cases, abnormal liver results go back to normal on their own within about three weeks. That's why a repeat test is often the first step.

Ranges vary by lab, age and gender. Different machines and methods give different numbers. Always compare your result with the range printed on your own report, and compare reports from the same lab where you can.

A normal result is not a full all-clear. Someone can have a serious liver condition and still get normal blood results. If you have risk factors, your doctor may suggest more tests anyway.

Liver function test results explained: the main markers

ALT (alanine aminotransferase)

ALT is an enzyme found mostly inside liver cells. When those cells are irritated or damaged, ALT leaks into the blood. That makes it the most liver-specific of the enzymes, and a high ALT is one of the most common flags on any report.

Mild rises are often temporary. Hard exercise or heavy drinking in the day or two before the test, a recent illness, and some medicines and supplements can all push ALT up for a while. Ongoing causes include fatty liver, viral hepatitis, alcohol and medicine-related liver injury.

AST (aspartate aminotransferase)

AST is also released when liver cells are stressed, but it is made in the heart, muscles and other tissues too. A high AST on its own could come from the liver, the heart or muscle.

The AST/ALT ratio

Doctors often look at the two enzymes together. According to Cleveland Clinic:

• Both raised by about the same amount fits causes other than alcohol, such as an infection or other toxins.
• AST about twice as high as ALT points more towards alcohol-related injury.

The ratio is a clue, not a verdict. It only means something when read with the rest of your results and your history.

ALP (alkaline phosphatase)

ALP comes mainly from the liver's bile ducts and from bone. A high ALP can mean bile isn't flowing freely, but it can also come from bone conditions. When ALP is raised on its own, doctors may check things like vitamin D before focusing on the liver.

GGT (gamma-glutamyl transferase)

GGT sits mostly in the liver and rises when the liver or bile ducts are damaged. A high GGT alongside a high ALP makes a bile-flow problem more likely. GGT is also sensitive to alcohol. In people who drink heavily, it should settle after about four weeks without alcohol, according to the NHS Specialist Pharmacy Service.

Bilirubin

Bilirubin is a yellow pigment made when old red blood cells break down. The liver clears it into bile. If it builds up, the skin and the whites of the eyes can turn yellow (jaundice).

A raised bilirubin with otherwise normal results is often Gilbert's syndrome, a common inherited trait. It can cause mild, on-and-off yellowing, often after poor sleep, dehydration, alcohol or over-exercising. The NHS says it doesn't damage the liver or shorten life.

Albumin and total protein

Albumin is a protein the liver makes. It helps keep fluid inside your blood vessels. Because it lasts about 20 days in the blood, it changes slowly. A low albumin together with other abnormal liver results can point to longer-term liver disease. But low albumin on its own is often not about the liver at all. Infection, inflammation, kidney problems and poor absorption of food can all lower it.

PT and INR (clotting time)

The liver makes clotting proteins, so some panels include prothrombin time (PT) or INR. A longer clotting time can come from liver disease, but also from warfarin or low vitamin K.

Typical adult ranges (examples only)

These are example ranges from published sources, one set in US-style lab units and one in UK-style units. U/L and IU/L mean the same thing. Your lab's range is the one that counts.

Marker	Example range (US-style units)	Example range (UK-style units)
ALT	7 to 56 U/L	0 to 40 IU/L
AST	10 to 40 U/L	0 to 35 IU/L
ALP	44 to 147 U/L	varies by lab method
GGT	varies by age and gender	0 to 50 IU/L
Total bilirubin	0.1 to 1.2 mg/dL	5 to 21 µmol/L
Albumin	3.5 to 5.0 g/dL	35 to 50 g/L

US-style figures are from Testing.com. UK-style figures are from the NHS Specialist Pharmacy Service, except AST, which is from Cleveland Clinic. Notice how much they differ even for the same marker.

Patterns matter more than any single number

Doctors rarely react to one marker in isolation. They look for patterns:

• Mostly ALT and AST raised: stress on the liver cells themselves.
• Mostly ALP and GGT raised: a possible problem with bile flow.
• Low albumin with a long clotting time: the liver may not be making enough proteins, which needs a closer look.
• Only bilirubin raised: often harmless, as with Gilbert's syndrome.

How far outside the range also matters. NHS guidance for professionals treats a result under twice the upper limit as mildly abnormal and usually worth repeating. Results more than two to three times the upper limit usually lead to further tests. Very high enzyme levels, above 1,000, can point to a sudden injury, such as from a medicine or a virus, and usually need specialist input quickly.

What usually happens next

If your liver results are off, your doctor may:

1. Repeat the test in a few weeks, sometimes after a break from alcohol.
2. Review your medicines and supplements, including anything you buy over the counter. Don't stop a prescribed medicine on your own.
3. Order more blood tests, such as hepatitis B and C checks or a scarring score called FIB-4.
4. Arrange a scan, such as an ultrasound or a FibroScan.
5. Refer you to a liver or gut specialist if results stay abnormal or the pattern is unclear.

Before the test, ask whether you need to fast. Some labs ask for 10 to 12 hours without food or drink; others don't need it for a liver panel alone.

Questions to ask about your results

• Which markers are outside the range, and by how much?
• Is this a liver cell pattern, a bile-flow pattern, or neither?
• Could my medicines, supplements, alcohol or recent exercise explain it?
• When should I repeat the test, and what would change the plan?

When to get urgent help

Call your local emergency number or go to an emergency department straight away if you are vomiting blood, your poo is very dark or black, or you suddenly become confused or have slurred speech. These can be signs of serious liver trouble, and yellow skin with sudden confusion is an emergency.

If your skin or the whites of your eyes turn yellow and you don't know why, get an urgent same-day appointment with a doctor.

Keeping track over time

Liver results are most useful as a trend. If you upload your reports to Saluvo, two AI models read each one, you confirm any value they disagree on, and you can see how markers like ALT or GGT move across reports before your next appointment. Your doctor still decides what it means.