Alanine Aminotransferase Blood Test (ALT)

What is an Alanine Aminotransferase Blood Test (ALT)?

An Alanine Aminotransferase (ALT) test estimates the levels of alanine aminotransferase (ALT) in your blood. Alanine aminotransferase is an enzyme, also known as Alanine transaminase (ALT), Serum glutamic-pyruvic transaminase (SGPT) or GPT. Enzymes are proteins that increase the speed of specific chemical reactions in your body.  Alanine aminotransferase is one of the two transaminases, the other being Aspartate aminotransferase (AST). ALT is more specific to liver damage than AST since it is found mainly in the liver, and AST is found in other organs such as the heart, muscles, and brain. ALT has a function to transport amino acids in the metabolic reactions occurring in the liver. It facilitates the breakdown of amino acids and promotes the synthesis of glucose.

An ALT blood test cannot identify the exact cause of liver disease. It can only show that your liver is being damaged. ALT enters the bloodstream due to leakage when your liver or bile duct is damaged. Your liver is crucial for producing proteins in your body, detoxification and metabolism. It also makes bile, a fluid that helps your body process fats in the process of digestion.

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Why is an Alanine Aminotransferase blood test done?

An Alanine Aminotransferase blood test is typically performed as part of a Liver Function Test.  Your doctor will recommend this test due to the following reasons:

• To review your overall health: As a component of a routine medical examination, and to monitor your general health.
• To diagnose a liver condition: In case you have symptoms of a liver disease, such as weakness, fatigue, jaundice, abdominal pain, nausea, vomiting, loss of appetite, and itching.
• To monitor the effects of treatment: In case you are being treated for hepatitis, the levels of ALT can indicate the effectiveness of the treatment.
• To determine levels in comparison with other liver enzymes: The ratio between alanine aminotransferase and aspartate aminotransferase is used as an indicator of liver damage. The ratio between AST and ALT is >2.0 for alcoholic hepatitis, 1.5 to <2.0 in acute viral hepatitis, and >1.0 in fibrosis and cirrhosis.

What conditions cause a change in the Alanine Aminotransferase blood levels?

High Alanine Aminotransferase levels

Elevated ALT is found in various conditions linked to liver and other organs:

Liver diseases

Liver conditions, including infection, and inflammation can cause an increase in the levels of ALT.

• Non-alcoholic fatty liver disease (NAFLD):  Obesity can cause fatty buildup in the liver, causing Non-alcoholic fatty liver disease (NAFLD). At this stage, there are no changes in liver cells.  This can progress to Non-alcoholic steatohepatitis (NASH) which is characterised by inflammation and changes in the liver cells.‍
• Alcoholic Liver Disease: Excessive alcohol intake causes liver damage, including alcoholic hepatitis, fatty liver, and cirrhosis, all of which can increase ALT levels. Drinking too much alcohol causes changes in serum ALT levels, which further impact the liver. High ALT is linked to various degrees of liver injury or a tendency to develop liver problems. ‍
• Viral hepatitis: Viral hepatitis is an inflammation of the liver caused by viruses that causes enzymes, including ALT, to be released into the bloodstream. The most common viruses for hepatitis include Hepatitis B and C. Hepatitis B virus has a wider range of risk factors than Hepatitis C and includes immigrants from endemic countries, human immunodeficiency virus infection, injection drug use, men who have sex with men, household contacts, or sex partners with the disease, and contact with the mother during childbirth. The risk factors for Hepatitis C virus comprise certain historical factors, including being born between 1945 and 1965, injection or intranasal drug use, blood transfusion before 1992, incarceration, hemodialysis, born to a mother with the disease, and unregulated tattoo.‍
• Cirrhosis: Cirrhosis occurs due to chronic liver damage from various causes, such as alcohol abuse or viral hepatitis.  This results in the formation of scar tissue that replaces healthy liver tissue, causing high ALT levels.‍
• Hereditary hemochromatosis: Hereditary hemochromatosis is a genetic disease causing increased iron absorption in the intestines and leading to an increase in iron concentration in the liver. Excess iron results in inflammation and changes in the liver, causing an increase in the ALT levels.‍
• Alpha1-Antitrypsin Deficiency: Alpha1-antitrypsin deficiency is a genetic condition that primarily causes chronic lung and liver disease. It leads to early-onset emphysema and elevations in liver enzymes, including ALT, or clinical findings of advanced liver disease without a known cause.‍
• Autoimmune hepatitis: Autoimmune hepatitis occurs more often in young women and is associated with other autoimmune disorders.‍
• Wilson’s disease: Wilson’s disease is related to ineffective copper metabolism. It usually occurs in people younger than 35 years, commonly of Eastern European descent. Kayser-Fleischer rings (copper deposition around the cornea) or mental health symptoms with changes in the liver are the main features of this condition.‍
• Liver tumours or cancer: Both primary liver tumours and metastatic tumours (cancer that has spread to the liver) can cause increased levels of ALT.

Conditions outside liver

Extrahepatic or conditions outside the liver can also cause an increase in the levels of ALT. These conditions, such as thyroid disorders, celiac disease, pancreatitis, and congestive heart failure, have been associated with elevated transaminase levels, including ALT.

Medications 

Certain medications such as acetaminophen, aspirin, lisinopril, isoniazid, methotrexate, bupropion, and anti-depressant medications can damage the liver, leading to the release of ALT into the bloodstream.  The damage to the liver is reversible if the exposure to the medication or toxin is discontinued at an early stage.

Low Alanine Aminotransferase levels

Low or normal levels of Alanine aminotransferase suggest that you are unlikely to have liver disease or recent alcohol consumption. Low ALT levels can also occur in chronic kidney disease or nutritional deficiencies such as vitamin B6.

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What factors affect the levels of Alanine Aminotransferase?

Physical exercise

Physical activity can temporarily raise your ALT levels, about 2 to 2.2-fold higher than the standard limit. While the cause of elevated ALT might not be liver-related, it is probably released from the exercising skeletal muscles.

Diurnal variation

ALT activity has a diurnal variation; the lowest value is at 4:00 am, and the peak value is in the evening at 4:00 pm.

Gender

ALT is higher in males compared to females. These gender-based differences in ALT levels are possibly related to hormonal differences between males and females.]

Ethnicity

Ethnicity affects your ALT levels. Mexican Americans have a greater increase in ALT levels than other ethnicities.

Body mass index

ALT levels have a positive correlation to body mass index. As the BMI increases, the ALT levels tend to rise.

How do you prepare for your Alanine Aminotransferase blood test?

Some things to consider before doing an Alanine Aminotransferase blood test include:

• Various medications and supplements can affect your liver and ALT levels. Talk to your doctor if you are taking medications.
• Intense physical activity can also impact ALT levels. So, inform your doctor in case you do vigorous workouts.

An alanine aminotransferase blood test is ordered as part of the Liver Function Tests (LFT). You are not required to fast for this test; however, you may be required to fast for 8-12 hours, depending on other tests you may have scheduled. It is recommended to stay hydrated by drinking enough water when fasting. Your doctor will let you know if you need to follow any special instructions.

How is an Alanine Aminotransferase blood test done?

The general steps of a blood test involve the following:

• A medical laboratory technician will check your arms for a vein that can be reached comfortably. This is usually in the inner part of your arm on the other side of your elbow
• Upon location of the vein, they would clean and disinfect the area
• They would then insert a small needle into your vein to draw a blood sample, which might feel like a slight pinch
• After they insert the needle, a small amount of blood will collect in a test tube
•  They will remove the needle and press the bleeding site with a cotton ball or gauze to stop the bleeding
• A bandage will be applied on the site and the collection of the sample will be done
• After a healthcare provider has collected your blood sample, they’ll send it to a laboratory for testing. Once the test results are back, your doctor will share the results with you

Interpretation of test results

The normal reference range of Alanine Aminotransferase for females is 5-20IU/L and for males is 5-30IU/L.

The values of ALT higher than the standard values in adults indicate an underlying condition associated mainly with the liver. Several factors can influence the levels of ALT in your body. Your doctor may repeat the test or recommend additional testing based on your signs and symptoms.

What can you do for elevated levels of Alanine Aminotransferase?

The initial management for high levels of Alanine Aminotransferase is based on dietary and lifestyle changes.

• Liver supportive diet: Liver support foods promote detoxification of the liver and regulate its function. These include green vegetables such as broccoli, mustard greens,  cabbage and brussel sprouts; root vegetables such as parsnips, carrots and burdock; dandelion greens; garlic, onion. Limit intake of red meat and avoid fried foods.
• Exercise: Include aerobic exercises and resistance training.
• Weight loss: Your risk of developing fatty liver and gallstones increases if you are overweight or have high cholesterol. Therefore, making efforts to achieve a healthy weight through diet and exercise is essential for optimal levels of ALT.
• Alcohol intake: Limit the intake of alcohol to no more than one drink per day for women and two drinks per day for men to prevent rise in levels of ALT. Many alcoholic beverages, including beer and wine, have high amounts of carbohydrates, so all alcohol intake must be included in your daily carbohydrate and calorie requirements.
• Smoking: Smoking increases the risk of cancer in the liver and bile ducts. So, talk to your healthcare provider if you require help in quitting smoking.
• Stress management: Use mindfulness practices like meditation and yoga to decrease stress levels that ultimately affect various body functions.
• Protect from chemicals: The use of harsh household chemicals and plastics can release fumes that enter your body through breathing and are ultimately detoxified by the liver. Avoid the use of strong synthetic chemicals at home and replace them with natural options.
• Protect from infections: The risk factors for transmission of hepatitis B and C, such as contaminated needles, unprotected sexual contact, and exposure during childbirth, must be taken into consideration and protection taken accordingly.
• Medications/natural supplements: Your doctor may also prescribe medications or natural supplements for liver support and protection.

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Sources:

1. Moriles KE, Zubair M, Azer SA. Alanine Aminotransferase (ALT) Test. [Updated 2024 Feb 27]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK559278/.

2. Oh RC, Hustead TR, Ali SM, Pantsari MW. Mildly Elevated Liver Transaminase Levels: Causes and Evaluation. Am Fam Physician. 2017;96(11):709-715.

3. Lala V, Zubair M, Minter DA. Liver Function Tests. [Updated 2023 Jul 30]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482489/.

4. Diabetes action research and education foundation. Liver. https://diabetesaction.org/article-liver.

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