Key takeaways
- Liver function tests are a panel of eight markers: ALT, AST, GGT, alkaline phosphatase, bilirubin, total protein, albumin and globulin.
- The pattern across the panel tells a doctor far more than any one number.
- Everyday things such as alcohol, some medicines and hard exercise can nudge the results. It helps to mention them when you have your blood taken.
- Your report shows the reference range beside each result, which makes a flagged marker easy to spot and easy to discuss with a doctor.
Your results have come back and one line, ALT, has a small H beside it. Or your GP's letter says your liver tests were a little raised, and nothing more. You want to know what that actually means.
Liver function tests check how your liver is working by measuring the enzymes, proteins and bilirubin it makes or processes. A raised ALT or AST usually points to inflammation or stress on liver cells. A raised alkaline phosphatase with GGT points more towards the bile ducts. The liver function tests panel at Blood London measures all eight markers together.
If you would rather skip the reading, book liver function tests at 117a Harley Street. It costs £72.50 plus the £50 blood draw (£122.50 total), with results in 1 day.
What does the liver function test panel actually check?
One blood sample covers eight markers: bilirubin, ALT, AST, total protein, alkaline phosphatase, albumin, globulin and GGT. Each one shows a different job the liver does. Bilirubin comes from breaking down old red blood cells. Albumin, globulin and total protein are blood proteins the liver makes. ALT, AST, alkaline phosphatase and GGT are enzymes that leak into the blood when liver cells or bile ducts are irritated.
Doctors look at the pattern across the panel. Different combinations of raised and normal markers point in different directions, so one figure seldom tells the whole story.
What does a raised ALT or AST mean?
A raised ALT or AST usually means liver cells are inflamed or under stress, and the two are often read together. ALT is found mostly in the liver, so it is a fairly specific marker of liver cell damage. AST is also found in muscle and the heart. A raised AST with a normal ALT can sometimes point away from the liver.
Common causes of a mild rise include fatty liver disease, alcohol and viral infection. Certain medicines can do it too, such as some statins or long-term painkillers. Even strenuous exercise beforehand can push the numbers up, which is why it helps to mention recent exercise or alcohol to the phlebotomist.
What does a raised GGT mean?
GGT is sensitive to alcohol and to bile duct problems, and it often rises before the other liver markers change. Regular drinking, some medicines and conditions affecting the bile ducts can all raise it, so it is usually read alongside ALT and AST.
If you specifically want a picture of recent drinking, Blood London's Alcohol Profile includes GGT within a wider set of markers, including PEth and CDT. It costs £261.25, with results in 5 to 7 days.
What does a raised bilirubin mean?
Bilirubin is a pigment made when red blood cells break down. The liver normally processes it and clears it in bile. A raised level can come from a liver or bile duct problem, or from red blood cells breaking down faster than usual. High levels cause jaundice, a yellowing of the skin or eyes.
A mildly raised bilirubin with otherwise normal liver markers is sometimes down to Gilbert's syndrome. That is a common and harmless variation in how the liver handles bilirubin, though it needs a doctor's assessment to confirm.
If you notice yellowing of the skin or eyes, dark urine or pale stools, see a doctor the same day. Go to A&E or call NHS 111 if you also feel very unwell, are vomiting repeatedly, or become confused.
| Marker | Where it comes from | Common reasons it is raised |
|---|---|---|
| ALT | Mostly found in liver cells | Fatty liver disease, alcohol, some medicines, viral infection |
| AST | Liver and other tissues, including muscle | Similar to ALT, plus recent strenuous exercise |
| GGT | Liver and bile ducts | Alcohol, some medicines, bile duct problems |
| Alkaline phosphatase | Liver, bile ducts and bone | Bile flow problems, bone conditions; normally higher in teenagers and in pregnancy |
| Bilirubin | Made when red blood cells break down | Liver or bile duct problems; Gilbert's syndrome |
| Albumin | Made by the liver | Reduced liver function or poor nutrition when low |
What does low albumin mean?
Albumin is a protein made by the liver that helps hold fluid in your blood vessels. A low level can reflect reduced liver function, poor nutrition, or a long-term illness elsewhere in the body. Total protein and globulin are read alongside it to give a broader picture.
A low albumin is a prompt for a closer look. If fatigue or unexplained weight change is also part of the story, it is often reviewed alongside your full blood count results.
Can alcohol or medicines affect my results without liver disease?
Yes. Alcohol in the day or two before the test can affect some results even when the liver is healthy. Certain medicines, a recent illness or strenuous exercise can also shift the markers for a while. Mention your recent drinking, any new medicines and recent exercise to the phlebotomist, so they can be taken into account when the results are reviewed.
How liver function testing works at Blood London
You can walk in or book online at 117a Harley Street, seven days a week, with no GP referral needed. No fasting is required. Results are usually back within 1 day and sent to you by email. Each test price on this page is plus the £50 blood draw, which is charged once per visit. It makes sense to add any other private blood tests in London at the same time.
If a viral cause needs checking, the Acute Viral Hepatitis Screen tests for hepatitis A, B and C for £175, with results in 1 day. You can add a doctor review of your report for £75. If anything sits outside the range, a GP appointment at Medical Express Clinic (£150) can look at the cause and any further tests.
When you are ready, start your booking for the liver function panel.
Frequently asked questions
Can liver function tests diagnose a liver disease on their own?
They flag a pattern. A doctor then interprets it alongside your symptoms, your history and sometimes further tests, such as a scan.
Do I need to fast before liver function tests?
No fasting is needed for this panel. If your doctor has given you a specific instruction, follow that.
How quickly will I get my liver function test results?
Results are usually back within 1 day, and they are sent to you by email.
Can exercise affect ALT or AST results?
Yes. Strenuous exercise shortly before the blood draw can temporarily raise AST in particular. That is one reason a single raised result is usually repeated before anyone acts on it.
Is a raised GGT always about alcohol?
Not always. GGT is sensitive to alcohol, but it can also rise with certain medicines and with bile duct problems. That is why it is read alongside the other markers.
What should I do if one of my liver markers is outside range?
Have a doctor look at it. You can add a doctor review to your test for £75. Or book a doctor's appointment to talk through the result, your symptoms and your history. A single marker just outside the reference range is common and often has a straightforward explanation, but it is still worth reviewing.
References
- NHS: Non-alcoholic fatty liver disease (NAFLD)
- NHS: Gilbert's syndrome
- British Society of Gastroenterology: Guidelines on the management of abnormal liver blood tests
- Lab Tests Online UK: Liver function tests
- British Liver Trust