Liver blood test guide: what your results may mean

Liver blood tests — sometimes called liver function tests or LFTs — are one of the most common blood panels in UK primary care and private health checks. They’re often included in routine health checks, sometimes added when a GP is investigating vague symptoms, and frequently come back with at least one marker outside the reference range. Many people discover an abnormal result while feeling completely well.

A small but important point: the name “liver function tests” is slightly misleading. The markers in this panel are blood substances that may reflect liver health, but they don’t directly measure how well the liver is doing its job. A normal result is reassuring; a raised result is a flag for further thought, not a diagnosis.

This guide explains what each marker means in plain English, what raised results may suggest, and — just as importantly — what these tests can’t tell you. If your results have come back raised and you’ve landed here looking for answers, please read this article as background information and also speak to your GP. They’re the right person to interpret your results in your full clinical context, and the rest of this guide will explain why that matters.

What a liver blood test measures

The exact panel can vary between labs, but it commonly includes:

• ALT (alanine aminotransferase) — an enzyme mainly found in the liver.
• AST (aspartate aminotransferase) — another enzyme found in the liver and in other tissues.
• ALP (alkaline phosphatase) — an enzyme found in bile ducts, bone and other tissues.
• GGT (gamma-glutamyl transferase, sometimes written as gamma-GT) — an enzyme associated with bile ducts.
• Bilirubin — a breakdown product of red blood cells, processed by the liver.
• Albumin — a protein made by the liver.
• Total protein — a combined measure of albumin and other proteins. Not every panel includes this.

These markers are interpreted together. Looking at one number in isolation rarely tells you much; the pattern across several markers is usually more informative.

ALT and AST explained

ALT and AST are enzymes that live inside liver cells. When liver cells are irritated or damaged, even mildly, small amounts of these enzymes leak into the blood, and levels can rise.

The two are often interpreted together, but they aren’t identical:

• ALT is more specific to the liver. A raised ALT usually points toward something happening in the liver itself.
• AST is found in the liver but also in muscle, heart and red blood cells. A raised AST can sometimes reflect non-liver causes, particularly after intense exercise or a muscle injury.

A raised ALT or AST is one of the most common findings on a routine blood test, and the British Liver Trust notes that mild and temporary rises are common and often don’t indicate serious liver disease. Causes can range from non-alcohol-related fatty liver disease (now sometimes called metabolic dysfunction-associated steatotic liver disease, or MASLD), to alcohol-related liver changes, certain viral infections, some medications, herbal supplements and several other conditions.

Reference ranges vary between labs, and what counts as a meaningful rise depends on how high the level is, how long it’s been raised, and what else is going on. A small isolated rise on one test often resolves on repeat testing and may not need any specific action beyond a recheck and a conversation with your GP.

If your ALT or AST has come back raised, the most useful next step is almost always a GP appointment — not extensive online research about specific liver conditions. Your GP can review your results alongside your symptoms, alcohol intake, medication, weight, family history and any other relevant context, and decide what (if anything) needs to happen next.

ALP and GGT explained

ALP and GGT are also enzymes, but they tell you about a different part of the liver story: the bile ducts.

ALP (alkaline phosphatase) is found in the liver and bile ducts, but also in bone, the placenta during pregnancy, and the intestines. That’s why a raised ALP isn’t automatically a liver issue. In young people who are still growing, raised ALP often reflects normal bone activity. In adults, it can reflect bone healing after a fracture or other bone conditions, as well as liver and bile duct causes.

This is where GGT (gamma-glutamyl transferase) becomes useful. GGT is closely associated with the bile ducts but not with bone. So GGT often helps clarify what a raised ALP means:

• A raised ALP with a raised GGT may suggest the cause is in the liver or bile ducts.
• A raised ALP with a normal GGT may suggest the cause is bone-related, growth-related, or something else.

GGT can also rise with regular alcohol use and with some medications. It isn’t a sensitive measure of any single thing — it’s a clue that fits into a wider pattern. Like ALT and AST, mild isolated rises are common and often resolve on repeat testing.

Bilirubin explained

Bilirubin is a yellow-orange substance produced when old red blood cells are broken down. The liver processes it and excretes it into bile, which then leaves the body through the digestive tract.

When bilirubin is significantly raised, it can cause jaundice — a yellowing of the skin or the whites of the eyes. Other signs to be aware of include unusually dark urine or pale stools.

A mildly raised bilirubin on a routine test isn’t always a problem. Around 5% of people in the UK have Gilbert’s syndrome, a benign and inherited variation in how the body processes bilirubin. It’s often discovered by accident on a routine blood test, particularly during a period of fasting, illness or stress, and usually doesn’t need any treatment.

That said, sudden or significant jaundice, dark urine, or pale stools should be discussed with your GP promptly. These can be signs of conditions that need timely investigation. If you’re unwell with these symptoms outside normal GP hours, NHS 111 can advise on next steps.

Albumin and total protein explained

Albumin is a protein made by the liver. It does a lot of work in the body, including helping fluid stay where it should and acting as a carrier for many substances in the blood.

A low albumin level can sometimes suggest that the liver isn’t producing as much as it should — what’s sometimes called reduced “synthetic function”. But there are other causes too: kidney disease, longstanding inflammation, poor nutrition, and certain other conditions can all lower albumin. In isolation, a slightly low albumin isn’t a specific finding.

Total protein measures albumin plus other proteins in the blood (mainly globulins). It can be useful in a wider clinical picture but isn’t specific on its own.

Not every liver panel includes albumin and total protein. If your panel does, treat them as additional context rather than the answer.

Common patterns and what they may suggest

Looking at the markers together is where the picture starts to come into focus. The patterns below are deliberately general — they describe what a clinician might consider, not a checklist to work through on your own:

• Predominantly raised ALT and AST may suggest a pattern of liver cell irritation (sometimes called a “hepatocellular” pattern). Many causes are possible, including non-alcohol-related fatty liver disease, alcohol-related liver changes, certain viral infections, and reactions to some medications or supplements.
• Predominantly raised ALP and GGT may suggest a pattern affecting the bile ducts or bile flow (sometimes called a “cholestatic” pattern). Causes can include gallstones, bile duct issues and reactions to certain medications.
• Raised bilirubin may suggest a problem with bilirubin processing or bile flow, or it can be a benign finding in people with Gilbert’s syndrome.
• Low albumin may suggest reduced liver synthetic function, but can also reflect kidney disease, inflammation or nutritional factors.

These are patterns of association, not diagnoses. The same pattern can have many different causes, and one set of results almost never gives a complete answer. Repeat testing, sometimes after a few weeks or months, and further investigation — often including ultrasound or other imaging, and sometimes specialist review — are routine next steps.

This is exactly why pattern interpretation is GP territory, not blog territory. A raised marker is the start of a conversation, not the answer to one. If your results show any of the patterns above, the right next step is a GP appointment.

What liver blood tests can’t tell you

It’s just as important to be clear about the limits of these tests. Liver blood tests:

• Don’t diagnose a liver condition on their own. Many mild rises resolve on repeat testing, and the same set of markers can have multiple possible causes.
• Don’t show the cause of a raised result. Several different conditions can produce a similar pattern, which is why GP review and sometimes imaging or specialist input are needed to work out what’s going on.
• Don’t show how much scarring (fibrosis or cirrhosis) is present. That generally needs imaging such as an ultrasound, specialised scans like FibroScan or transient elastography, or specialist assessment.
• Don’t replace your GP’s judgement or the input of a specialist clinic where one is appropriate.

If your liver markers are outside the reference range, please speak to your GP. They can repeat the tests, review your medications, supplements and alcohol intake, ask about symptoms, and arrange imaging or referral if needed. A private blood test is information that can support a conversation; it isn’t a diagnosis.

Fasting, alcohol and medication

A few practical points worth knowing:

• Fasting is usually not required for liver blood tests. If your appointment includes other tests that need fasting (some lipid panels in particular settings), the clinic will tell you in advance. For broader prep advice, see our eating before a blood test guide.
• Recent alcohol intake can affect liver markers in the short term. GGT in particular can rise with regular drinking, and a heavier drinking session in the days before a blood test can sometimes nudge results upward. That doesn’t mean a single occasion is a permanent change — it’s one of the reasons repeat testing is often useful.
• Medications and supplements can also affect liver enzymes. This includes some prescribed medications and, importantly, herbal supplements and over-the-counter products. Don’t stop any prescribed medication without medical advice. If you take supplements — particularly herbal products — it’s worth telling your GP, as they’re a more common cause of liver enzyme rises than many people realise.

Should you book a single liver blood test or a broader health check?

This depends on what you’re trying to understand.

A single liver blood test may make sense if:

• Your GP has previously advised you to monitor liver markers and a repeat panel would be useful information.
• You want a focused check on the liver markers themselves.
• You already have a wider clinical picture in place.

You can read more on the liver function test page.

A broader health check may make more sense if:

• You want liver markers interpreted alongside related tests — a full blood count, kidney function, cholesterol and blood sugar — because liver-related symptoms can overlap with other causes.
• You don’t yet have a wider baseline and would rather look at liver function as part of a fuller picture.
• You’d prefer a structured review with time to discuss multiple aspects of your health in one appointment.

In that case, the Advanced Health Check is a natural fit. If you want the broadest standard overview, the Optimal Health Check is also worth considering. The cholesterol results explained, HbA1c blood test guide and kidney function blood test posts cover related markers, and our 5 essential blood tests for adults guide is a good starting point if you’re new to blood testing.

If you’re not sure which option suits you, contact us and we can help you choose.

When to speak to your GP

Speak to your GP if any liver markers are outside the lab reference range, even mildly. Mild rises are common and often turn out to be unimportant, but the only way to know is for someone with your full clinical picture to look at them.

Speak to your GP promptly if you have:

• Yellowing of the skin or the whites of the eyes (jaundice)
• Dark urine or unusually pale stools
• Significant abdominal pain, particularly on the right side
• Persistent vomiting
• Unexplained weight loss
• Persistent unusual fatigue

It’s also worth speaking to your GP earlier rather than later if you have risk factors that increase the relevance of a raised liver marker, including:

• Heavier alcohol use, current or past
• Possible exposure to viral hepatitis
• Raised BMI or obesity
• Features of metabolic syndrome — for example raised waist measurement, high blood pressure, raised blood sugar or raised triglycerides
• A family history of liver disease
• Current or recent use of medications, herbal supplements or recreational drugs known to affect the liver

A private health check is designed for adults who currently feel well or want a baseline. It can usefully complement NHS care and help you prepare for a more focused conversation with your GP. It doesn’t replace medical care if you’re unwell.

In a life-threatening emergency — severe abdominal pain, confusion, vomiting blood, severe jaundice — call 999 immediately. For urgent advice that isn’t an emergency, NHS 111 is available online or by phone.

A useful piece of information, not the whole answer

Liver blood tests are useful because they can flag patterns that may benefit from further investigation. ALT, AST, ALP, GGT, bilirubin and albumin each add useful context. Looking at them together — and alongside your symptoms, history and other tests — is what makes them informative.

But they’re still markers, not a diagnosis. A raised result is the start of a thoughtful conversation, not the end of one. If you want to check liver markers as part of a broader review, the Advanced Health Check is a strong option, and why health screening matters sets out our wider thinking on what blood tests can and can’t do.

If you’re unsure which option is right for you, contact us and we can help you find the most appropriate starting point. Appointments are available from our Kingston upon Thames and Crawley clinics.