Liver function blood tests: results, normal ranges, and what they mean

If you’ve been told you need a liver function blood test, or you’ve just received your results, it’s normal to feel a bit uneasy. Liver tests often sound more serious than they are. In reality, they’re one of the most common blood tests used in routine healthcare, and most abnormal results turn out to be mild, temporary, or easily explained.

What is a liver function blood test?

A liver function blood test, often called an LFT, is a group of blood markers that give doctors insight into how your liver is coping.

Despite the name, not every marker measures liver “function” directly. Some show signs of liver stress or irritation, while others reflect how well the liver is carrying out certain jobs like making proteins or processing waste.¹

Doctors use liver blood tests to:

• Check liver health as part of a routine health review

• Monitor the effects of medication

• Investigate symptoms like fatigue, nausea, or jaundice

• Follow up on previous abnormal results

An LFT can’t diagnose a specific liver condition on its own, but it can help decide whether further tests or monitoring are needed.¹

Who should get a liver blood test?

Liver function tests are commonly ordered even when someone feels well. You might be offered one if you:

• Are having a routine health check

• Take medication that’s processed by the liver

• Drink alcohol regularly or previously did

• Have risk factors for fatty liver disease

• Have symptoms like ongoing tiredness, abdominal discomfort, or unexplained weight changes

Many people with early liver changes have no symptoms at all, which is why blood testing can be useful.

What does a liver function test measure?

An LFT usually includes a mix of enzymes, proteins, and pigments. Together, they help build a picture of liver health.¹

Liver enzymes

Enzymes leak into the blood when liver cells are under strain. A raised level doesn’t automatically mean permanent damage.

Proteins and pigments

• Bilirubin: A waste product from red blood cells. Raised levels can cause yellowing of the skin or eyes.¹

• Albumin: A protein made by the liver that helps maintain fluid balance.¹

• Total protein: Reflects overall protein production and immune activity.¹

These markers are more closely linked to the liver’s actual working capacity.

*Reference ranges vary slightly by lab.

Interpreting your results

Raised ALT or AST levels are common and often mild. They can be associated with:¹

• Fatty liver disease (NAFLD)

• Recent alcohol intake

• Certain medications

• Viral illness

• Intense exercise

Doctors look at patterns rather than single numbers. For example, ALT-predominant rises often point to fatty liver or inflammation, while an AST-to-ALT ratio can provide clues about alcohol-related effects, but no diagnosis is made from ratios alone.¹

Borderline or slightly raised results

“Borderline” usually means levels are less than twice the upper limit of normal. These often settle on repeat testing.

Temporary causes include:¹

• Illness or infection

• Alcohol in the days before testing

• Heavy exercise

• Certain medications

This is why repeat tests are common and not a cause for alarm.

Abnormal bilirubin or protein levels

Changes in bilirubin, albumin, or clotting markers can suggest the liver is under more sustained pressure. When this happens, doctors typically recommend follow-up testing or imaging to understand the cause.¹

Preparing for a liver function blood test

Do I need to fast?

Usually, no. Most liver blood tests don’t require fasting. However, if your test is combined with cholesterol or glucose checks, fasting may be advised.

How long do results take?

Results for a Numan blood test which includes LFTs are often available within a few days and can be obtained directly from the Numan app. They’re always reviewed alongside your medical history, lifestyle factors, and any symptoms.

Improving your liver health

The liver is remarkably resilient. In many cases, raised or borderline liver markers improve with small, steady changes rather than drastic interventions. It responds best to consistency over time.

Gradual weight loss, if needed

Excess body fat, particularly around the abdomen, is closely linked to fatty liver changes. Even modest, sustained weight loss can reduce fat stored in the liver and improve enzyme levels. Rapid or extreme weight loss, however, can place additional stress on the liver, so slower, steady progress is usually more supportive.²

Reducing alcohol intake

Alcohol is processed directly by the liver, and regular intake can raise liver enzymes even in people who don’t consider themselves heavy drinkers. Cutting back, spacing out drinking days, or taking alcohol-free periods often leads to noticeable improvements in blood test results within weeks to months.³

Balanced nutrition and regular movement

A varied diet that supports stable energy levels, alongside regular movement, helps reduce liver stress indirectly by improving insulin sensitivity and fat metabolism.⁴ There’s rarely a need for extreme diets, cleanses, or detoxes - the liver already does that job very effectively on its own.

Managing blood sugar and cholesterol

High blood sugar and abnormal cholesterol levels often travel alongside liver changes. Improving these through lifestyle adjustments or appropriate medical support can reduce the workload placed on the liver and improve test results over time.⁵

The numan take

Because liver changes often develop quietly and without obvious symptoms, periodic blood testing can be a helpful way to track trends rather than react once something feels wrong. Looking at patterns over time allows clinicians to spot early shifts and guide next steps calmly and appropriately.

If you want clarity and peace of mind, a Complete Blood Test can help you understand your liver health in context, with results reviewed by a clinician and explained clearly, so you know what matters now and what to keep an eye on going forward.

Important:

This article is for informational purposes only and doesn't replace medical advice. A liver function blood test can’t diagnose disease on its own, and results should always be discussed with a healthcare professional.

References

1. Lala V, Zubair M, Minter DA. Liver function tests. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2025.

2. Brunner KT, Henneberg CJ, Wilechansky RM, Long MT. Nonalcoholic fatty liver disease and obesity treatment. Curr Obes Rep. 2019;8(3):220–8.

3. Asrani SK, Mellinger J, Sterling S, Lucey MR, Bradley KA, Bhala N, et al. Reducing alcohol-associated liver disease burden in the general population. Lancet Gastroenterol Hepatol. 2025;10(12):1117–31. 

4. Tsompanaki E, Thanapirom K, Papatheodoridi M, Parikh P, Chotai de Lima Y, Tsochatzis EA. Systematic review and meta-analysis: The role of diet in the development of nonalcoholic fatty liver disease. Clin Gastroenterol Hepatol. 2023;21(6):1462-1474.e24.

5. Jin X, Xu J, Weng X. Correlation between ratio of fasting blood glucose to high density lipoprotein cholesterol in serum and non-alcoholic fatty liver disease in American adults: a population based analysis. Front Med (Lausanne). 2024;11(1428593):1428593.