Quick Guide

A liver function test (LFT) is a blood panel that measures enzymes and proteins to check how well your liver is working. It covers 10 markers from a single blood sample, processed at a CLIA-certified lab.

If you’ve been dealing with fatigue, yellowing skin, or stomach pain on the upper right side of your abdomen, a liver function test can help figure out whether the liver is involved. If your results come back high or low, your provider will read them alongside your symptoms and health history before recommending next steps.

About the Liver Function Test

Purpose of the test

A liver function test checks for signs of liver damage, inflammation, or reduced function. These tests are also called liver chemistries or liver tests, and they reflect liver injury and status more than they directly measure liver function. It’s one of the most common blood panels ordered during routine care and when symptoms could point to liver disease. According to the National Institute of Diabetes and Digestive and Kidney Diseases, liver disease encompasses a wide range of conditions that can damage the liver and reduce its ability to function.

Your liver handles hundreds of jobs. It filters toxins from the blood, makes proteins that help blood clot, produces bile to digest fat, and processes medications. When something goes wrong, certain enzymes and proteins shift in ways the test can pick up. Most liver conditions don’t cause obvious symptoms early on, so testing matters even when you feel fine.

The test serves three purposes:

  • Screening: Liver markers are often part of broader metabolic panels during routine checkups, catching early changes before symptoms show up.
  • Diagnosis: Ordered when symptoms like jaundice (yellowing of the skin or eyes), dark urine, fatigue, or upper right abdominal pain suggest a liver problem.
  • Monitoring: Tracks how well treatment is working for hepatitis, fatty liver disease, or cirrhosis (advanced liver scarring), and watches for liver-related side effects from medications.

The LFT doesn’t diagnose a specific condition on its own. Results are read alongside your symptoms, history, and sometimes imaging. It doesn’t measure clotting function (prothrombin time), gamma-glutamyl transferase (GGT), or markers specific to hepatitis viruses. Those require separate tests.

What does the liver function test measure?

This panel covers 10 markers from a single blood sample at a CLIA-certified lab. As explained by MedlinePlus, these markers reflect different aspects of how the liver processes waste, makes proteins, and responds to injury.

Routine Chemistry

  • Alanine aminotransferase (ALT/SGPT): An enzyme found mainly in liver cells that rises when liver cells are damaged or inflamed.
  • Albumin: A protein the liver makes to help keep fluid inside blood vessels and carry substances through the bloodstream.
  • Albumin/Globulin Ratio: A calculated comparison of albumin to globulin, reflecting the balance of proteins from the liver and immune system.
  • Alkaline phosphatase (ALP): An enzyme in the liver, bones, and bile ducts that rises when bile flow is blocked or liver tissue is damaged.
  • Aspartate aminotransferase (AST/SGOT): An enzyme in the liver, heart, and muscles that leaks into the blood when these tissues are injured.
  • Bilirubin, Total: The overall level of bilirubin, a yellow waste product from red blood cell breakdown that the liver processes and removes.
  • Bilirubin, Direct: The portion of bilirubin the liver has already processed (conjugated) and prepared for removal into bile.
  • Bilirubin, Indirect: The unprocessed portion of bilirubin still circulating before the liver converts it.
  • Globulin: A group of blood proteins that includes immune proteins, calculated by subtracting albumin from total protein.
  • Total Protein: The combined level of all blood proteins, mainly albumin and globulin, reflecting how well the liver makes protein.

When should I get a liver function test?

Consider testing if any of these apply:

  • Yellowing of the skin or eyes (jaundice)
  • Fatigue, nausea, or loss of appetite without a clear cause
  • Dark urine or pale, clay-colored stools
  • Pain or swelling in the upper right abdomen
  • A known risk factor for liver disease (heavy alcohol use, obesity, type 2 diabetes, or metabolic syndrome)
  • Current use of medications that can affect the liver, like statins, high-dose acetaminophen, or certain antibiotics
  • A family history of liver disease, including hereditary conditions like hemochromatosis or Wilson’s disease
  • A prior diagnosis of viral hepatitis B or C

If you’re experiencing yellowing of the eyes or skin, seek care promptly. That symptom can point to hepatitis or another condition that needs more than a routine blood panel.

For routine screening, liver function markers are often included in a comprehensive metabolic panel (CMP) during annual checkups. Your provider may order a standalone LFT if you’re starting a medication known to affect the liver, or if a previous panel showed borderline results worth watching.

How It Works

How to get tested

A liver function test is ordered through a health care provider, clinic, or hospital lab. Most providers send the order to CLIA-certified labs, where a standard blood draw is all that’s needed. Results come back through the ordering provider’s patient portal or office.

Testing.com connects you with CLIA-certified laboratory partners including LabCorp and Quest Diagnostics for in-lab blood draws. If you have questions about what your results mean or whether you need follow-up testing, your provider is the right person to walk through them with you.

Before the test

Your provider will tell you how to prepare. This panel does not require fasting. Water is generally fine unless told otherwise.

Tell your provider about all medications and supplements you’re taking. Statins, acetaminophen (especially at higher doses), NSAIDs like ibuprofen, certain antibiotics (amoxicillin-clavulanate is a leading cause of drug-induced liver injury), and herbal supplements like kava and green tea extract can all raise liver enzyme levels. Your provider may ask you to hold certain medications before the draw or will factor them into how your results are read.

Avoid intense exercise for 24 hours before the test. Hard workouts raise AST because AST is also found in muscle tissue. A post-workout spike can look like liver damage on paper. ALT can rise too, though less so, and a CK (creatine kinase) test helps confirm whether the source is muscle rather than liver.

During the test

  • Check in at the lab or patient service center with a photo ID and any order confirmation from your provider.
  • A phlebotomist (blood draw specialist) cleans a spot on your inner arm with antiseptic and draws blood from a vein. You’ll feel a brief pinch.
  • The draw takes less than two minutes. A small bandage covers the site afterward.

The whole visit runs about 15 minutes. Some people notice light bruising at the draw site over the next day or two. That’s normal. Keep the bandage on for at least 15 minutes. Call your provider if you notice pain that doesn’t go away, swelling, or redness at the site.

After the test

Results are typically ready within one to three business days after the lab receives your sample, though timing can vary by lab. You’ll get them through the ordering provider’s patient portal or office. If you haven’t heard back in three business days, contact the provider’s office directly.

What Do My Results Mean?

The LFT reports 10 separate values. Some markers are concerning when they’re high (ALT, AST, ALP, bilirubin). Others are concerning when they’re low (albumin, total protein). Your provider reads the full picture together, not each number on its own.

Typical reference ranges are listed here. These are approximate and vary by lab, age, sex, and testing method.

Reference ranges vary between labs. Some evidence suggests a healthy-normal ALT is lower than many labs’ stated upper limits (roughly 29 to 33 U/L for men and 19 to 25 U/L for women), so a result above those but within the lab range may still be worth discussing with your provider. Always compare your results to the lab’s own reference intervals on your report.

If your results are normal

All 10 markers fall within the lab’s reference range, which may suggest your liver is handling its workload without signs of damage. Normal results don’t rule out every liver condition, but they’re reassuring. If symptoms continue despite normal results, your provider may look at other causes or order follow-up imaging.

If your results are abnormal

One or more values outside the reference range doesn’t automatically mean serious liver disease. Mildly high results can come from recent intense exercise (AST), a medication you’re taking, a recent illness, or normal biological variation. Your provider will look at which markers are off and by how much.

Patterns matter more than single values. High ALT and AST with normal or mildly high ALP points toward liver cell damage, seen in viral hepatitis, metabolic dysfunction-associated steatotic liver disease (MASLD, formerly called nonalcoholic fatty liver disease), and alcohol-related liver disease. The AST-to-ALT ratio can offer a clue: a ratio above 2:1 is associated with alcohol-related liver disease, as described by the Merck Manual, while viral hepatitis tends to show ALT higher than AST.

High ALP with normal or mildly high ALT and AST suggests a bile duct problem or cholestasis (blocked bile flow). Isolated high unconjugated (indirect) bilirubin with normal enzymes can indicate Gilbert syndrome, a benign genetic condition that affects how the liver processes bilirubin.

Low albumin or low total protein points to reduced liver function, which can happen in chronic liver disease, malnutrition, or inflammatory conditions. The MedlinePlus albumin blood test resource notes that low albumin levels can reflect not only liver disease but also kidney disorders and poor nutrition.

A single abnormal result usually leads to repeat testing before any diagnosis. If repeat results are still off, your provider may order a hepatitis panel, imaging like an ultrasound, or a more specific marker like GGT. One abnormal value isn’t a diagnosis. It’s a starting point.

FAQs

What causes a liver function test to be high?

High liver enzyme results (ALT, AST, ALP, or bilirubin) have many possible causes. Common ones include fatty liver disease, viral hepatitis, alcohol use, medications like statins or high-dose acetaminophen, herbal supplements, and recent intense exercise. The NIDDK’s overview of liver disease notes that many liver conditions progress without obvious symptoms, making enzyme elevations an important early signal. Mildly high results sometimes reflect a temporary change rather than ongoing liver damage. Your provider will look at which markers are high and by how much before deciding on follow-up testing.

What are normal liver function test levels?

Normal ranges vary by lab, but typical values are: ALT 7–56 U/L, AST 10–40 U/L, ALP 44–147 U/L, total bilirubin 0.1–1.2 mg/dL, albumin 3.5–5.0 g/dL, and total protein 6.3–8.2 g/dL. Your lab report will show its own reference intervals next to your results. Read your numbers against those, not general guidelines.

What's the difference between ALT and AST?

ALT is found mainly in the liver, so a high ALT is a more specific signal of liver cell damage. AST lives in the liver too, but also in muscles, the heart, and red blood cells, so it can rise from causes outside the liver. When both are high, the AST-to-ALT ratio helps narrow down what’s going on.

Does a liver function test show cirrhosis or fibrosis?

Not directly. The LFT can show patterns that suggest chronic liver damage, but it can’t stage fibrosis (scarring) on its own. Low albumin, high bilirubin, and abnormal enzyme patterns together can raise concern for advanced disease. Staging fibrosis requires other tools: a FIB-4 score (calculated from age, AST, ALT, and platelet count), imaging like FibroScan, or in some cases a liver biopsy.

Is a liver function test the same as a comprehensive metabolic panel?

Not exactly. A CMP includes liver markers (ALT, AST, ALP, bilirubin, albumin, total protein) along with kidney markers, electrolytes, and glucose. A standalone LFT focuses on liver-specific markers. The CMP is broader; the LFT goes deeper on liver function by including direct and indirect bilirubin and the albumin/globulin ratio.

Can medications affect my liver function test results?

Yes. Statins, acetaminophen, NSAIDs, certain antibiotics, antifungals, and herbal supplements like kava and green tea extract can all raise liver enzyme levels. Tell your provider about everything you’re taking before the test. Don’t stop any prescription medication without checking first.

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