Liver Function Tests
Overview
Liver function panels include several blood tests that assess how well the liver is working and whether any damage has occurred. Doctors use these tests to detect liver problems early and to monitor changes over time.
- ALT (alanine transaminase)
- AST (aspartate transaminase)
- ALP (alkaline phosphatase)
- Bilirubin
Transaminasesโlike ALT and ASTโmay rise if liver cells are damaged. However, elevated liver enzymes do not always indicate liver disease. A healthcare provider interprets the results in context.
| Test Name | What It Measures |
|---|---|
| ALT/AST | Liver cell injury (enzymes) |
| ALP | Bile duct, liver, and bone |
| Bilirubin | Waste breakdown by liver |
Reasons for Testing
Doctors may order liver blood tests to check for infections, such as hepatitis B and hepatitis C, or to evaluate for liver damage or scarring caused by chronic conditions like cirrhosis. These tests also help monitor whether treatments for viral hepatitis or other forms of liver disease are working.
Liver blood tests are also useful for detecting side effects of medications. Certain medicines can harm the liver, so regular testing helps identify changes early and may prevent more serious complications. When the liver is damaged, certain substances in the blood may rise or fall.
By analyzing these changes, doctors can better understand the underlying issue. The pattern of results can help pinpoint conditions such as hepatitis, bile duct obstruction, or other liver-related problems. Common uses for liver blood tests include:
| Purpose | Example Condition |
|---|---|
| Find Infections | Hepatitis B, Hepatitis C |
| Monitor Ongoing Illness | Chronic liver disease |
| Check Medication Effects | Side effects from prescription |
| Test for Scarring or Damage | Cirrhosis |
| Measure How Well Liver Works | Jaundice, general liver health |
Types of Liver Blood Tests
Doctors examine these tests together to get a clearer picture of what is happening in the body.
- Alanine Transaminase (ALT) and Aspartate Transaminase (AST): Show if liver cells are being injured.
- Alkaline Phosphatase (ALP) and Gamma-Glutamyltransferase (GGT): Indicate problems with bile flow or blockages in the liver.
- Albumin and Total Protein: Reveal if the liver is making enough proteins.
- Bilirubin: Detects trouble with how the liver processes waste.
- L-lactate Dehydrogenase (LD): Signals liver stress or damage.
- Prothrombin Time (PT): Measures how long blood takes to clot, which relies on healthy liver function.
Additional Details
Liver blood tests uncover a wide range of health conditions. For example, doctors use them to investigate rare and common illnesses, including acute liver failure, alcoholic hepatitis, and nonalcoholic fatty liver disease.
These tests may also help diagnose inherited problems like Wilson’s disease or hemochromatosis, both of which affect how the body handles certain minerals. Doctors sometimes use liver tests to find certain cancers, such as liver cancer or bile duct cancer.
These tests can also support the diagnosis of autoimmune conditions, such as lupus or primary sclerosing cholangitis. Other diseases that might affect the liver, like HIV/AIDS, may be detected by these blood marker changes.
In children and adults who are overweight or have other risk factors, doctors use liver tests to check for signs of fatty liver disease. Some mental health disorders, like anorexia nervosa, may also change liver test results.
Possible Risks
Most risks of liver function testing are minor. The most common effects include mild soreness or bruising at the needle site. In rare cases, bleeding or swelling may occur.
People with chronic liver conditions, diabetes, or those who drink alcohol may have a slightly higher risk of bruising or slower blood clotting after the test.
Getting Ready for Testing
Before a liver function test, your doctor may advise you to stop eating and skip certain medicines. This helps avoid anything that could change the results.
Tip: Make a list of all medicines and supplements to share with your provider. Ask questions in advance if you are unsure about any instructions.
What You May Experience
A health professional uses a fine needle to draw blood from a vein, usually at the bend of your arm. This is quick and you may notice a slight pinch or stinging feeling. After the needle is removed, you may feel mild soreness for a short time where the needle went in.
Test Findings
Liver function tests measure how well the liver is working. These tests check different blood markers to provide a full view of liver health, including enzymes, proteins, and other chemicals made or processed by the liver.
Standard Ranges for Common Liver Markers
| Test Name | Normal Range (Adult Males) |
|---|---|
| ALT (Alanine transaminase) | 7 โ 55 U/L |
| AST (Aspartate transaminase) | 8 โ 48 U/L |
| ALP (Alkaline phosphatase) | 40 โ 129 U/L |
| GGT (Gamma-glutamyl transferase) | 8 โ 61 U/L |
| LD (Lactate dehydrogenase) | 122 โ 222 U/L |
| Albumin | 3.5 โ 5.0 g/dL |
| Total Protein | 6.3 โ 7.9 g/dL |
| Bilirubin (Total) | 0.1 โ 1.2 mg/dL |
| PT (Prothrombin time) | 9.4 โ 12.5 seconds |
Please note that these ranges can differ slightly by laboratory, age group, and sex.
Enzyme Measurements
ALT and AST levels indicate possible liver cell damage. When these numbers are higher than normal, this may suggest swelling, injury, or liver disease. ALP and GGT levels help identify issues with the bile ducts or possible blockages.
Heavy alcohol use or certain medicines may also raise GGT. High LD values can point to general cell injury, including damage to liver cells.
Protein Values
Albumin and total protein measure how much protein the liver is making. Low albumin may signal liver disease, kidney problems, or poor nutrition. Total protein includes albumin and other proteins in the blood. Changes in total protein can signal problems with liver function, infections, or other health issues.
Bilirubin Levels
Total bilirubin measures the breakdown of products from red blood cells processed in the liver. High bilirubin levels can cause yellowing of the skin and eyes (jaundice) and may indicate problems such as liver disease or bile duct obstruction.
Clotting Function
Prothrombin time (PT) shows how quickly blood clots form. A longer clotting time could mean the liver is having trouble making proteins needed for clotting. This information is key for managing both bleeding risks and liver conditions.
Other useful markers sometimes checked include the international normalized ratio (INR) for clotting, as well as alpha-fetoprotein (AFP), which helps detect certain tumors or liver cancers.
Doctors review these test results, symptoms, and other findings to decide if more tests or treatments are necessary. If someone already has diagnosed liver disease, repeat tests show if the condition is improving or worsening and how well treatments are working.
