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Liver Function Tests
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

Liver Function Tests

Liver function tests are blood tests that measure specific enzymes and proteins to assess liver health and detect potential damage or disease.

What are liver function tests?

Also known as a liver panel, these tests measure substances produced or processed by the liver to evaluate its function. Common measurements include:

  • Albumin and Total Protein: Proteins produced by the liver.
  • Enzymes (ALP, ALT, AST, GGT, LDH): Proteins that speed up chemical reactions; elevated levels often indicate liver damage.
  • Bilirubin: A waste product from broken-down red blood cells that the liver removes.
  • Prothrombin time (PT): A measure of how long it takes blood to clot, which relies on proteins made by the liver.

Other names: liver panel, liver function panel, liver profile, hepatic function panel, LFT

What are they used for?

These tests help providers determine if liver disease is causing symptoms, monitor the progression of known liver conditions, evaluate the effectiveness of treatments, or check for side effects of medications that may impact the liver.

Why do I need liver function testing?

Liver tests are often part of a comprehensive metabolic panel (CMP) during routine checkups. You may specifically need them if you exhibit symptoms of liver damage, such as:

  • Jaundice (yellowing of skin/eyes)
  • Nausea, vomiting, or lack of appetite
  • Fatigue or weakness
  • Abdominal pain or swelling
  • Dark urine or light-colored stool
  • Frequent itching

Testing is also recommended for those at high risk, including individuals with a family history of liver disease, alcohol use disorder, obesity, diabetes, or those taking medications known to affect the liver.

What happens during the test?

A health care professional will collect a blood sample from a vein in your arm using a small needle. The procedure typically takes less than five minutes.

Preparation and Risks

You will likely need to fast for 10–12 hours before the test. Inform your provider of all medications you are taking, as some can affect results, but do not stop taking them unless instructed. Risks are minimal, limited to slight pain or bruising at the needle site.

What do the results mean?

Interpreting liver function tests is complex, as providers must look for patterns across all measured substances. Abnormal results do not always indicate liver disease; they can be temporary or caused by other conditions, such as bone disease. Your provider will evaluate your results in the context of your symptoms, medical history, and current medications to determine if further testing is required.

Frequently Asked Questions

Elevated ALT and AST usually point to liver cell injury, but they can also rise with muscle damage or heart issues. A single mild rise may not be concerning, but persistent elevations or a pattern where ALT is much higher than AST often suggests hepatitis, fatty liver, or medication‑induced damage. Your clinician will compare the numbers to your baseline, look at other enzymes (ALP, GGT), and consider symptoms or risk factors before deciding on further tests or treatment.
High bilirubin can cause jaundice (yellowing of skin or eyes), dark urine, pale stools, and itching. It usually means the liver is not clearing bilirubin efficiently, which can happen with hepatitis, bile duct blockage, or hemolysis. If you notice any of these signs, let your provider know right away, as it may require imaging or a liver biopsy.
If you are on a statin, most guidelines recommend checking LFTs at baseline, then at 4–12 weeks, and annually if stable. For regular acetaminophen use (≤3 g/day), a baseline test and a repeat after 3–6 months is reasonable. If you experience muscle pain, fatigue, or jaundice, get an LFT sooner.
lcohol, high‑fat meals, or certain supplements (e.g., vitamin A, iron) can transiently raise liver enzymes. To avoid false elevations, avoid alcohol for at least 48 hours, skip large meals and fatty foods 12 hours before the draw, and inform your provider of any supplements. This helps ensure the results reflect your true liver health.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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