High ALT Levels Explained: Causes, Symptoms, and Key Biomarkers

According to the Centers for Disease Control and Prevention, liver health is a concern for 4.5 million adults in the United States. Alanine aminotransferase (ALT) is an important biomarker for liver health and function, particularly in early stages when symptoms may not yet be present. 

The American Gastroenterological Association notes that up to 4% of asymptomatic individuals may show elevated liver enzymes on testing, highlighting the silent progression of liver conditions. Recognizing the significance of elevated ALT levels is essential for timely evaluation and management, and for supporting liver health in at-risk individuals.

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What Is ALT (SGPT) in Blood Tests?

Alanine aminotransferase (ALT), formerly called serum glutamic pyruvic transaminase (SGPT), is an enzyme primarily found in the liver but also the kidneys, heart, and muscles. ALT helps turn the amino acid alanine into pyruvate. Pyruvate then goes into the Krebs cycle (also known as the citric acid or TCA cycle), which is a series of reactions that produce energy for cells. (13)   

ALT is one of the key biomarkers included in liver function panels. Under normal conditions, ALT levels in the bloodstream are low. However, when the liver is inflamed or not functioning optimally, ALT may leak out of liver cells and into the bloodstream, causing its levels to rise. (13) 

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What Does High ALT Mean in a Blood Test?

ALT is an important marker of liver function because it is more specific to liver cells than other hepatic biomarkers, such as alkaline phosphatase (ALP) and aspartate aminotransferase (AST). Elevated ALT levels are more directly associated with liver health, making it a useful indicator.

The normal range for ALT is 4-36 U/L. ALT levels may be slightly higher in older adults. Normal value ranges may vary between different laboratories.

Elevated serum ALT most commonly indicates liver cell stress, which could be due to many causes (discussed in more detail below). Because ALT isn't just found in the liver, elevated ALT levels can also indicate stress to cells in other parts of the body.

What Causes High ALT Levels?

Having high ALT levels doesn't necessarily mean you have a medical condition requiring treatment. Approximately one-third of people with elevated liver enzymes will see their levels return to normal within two to four weeks.

 Elevated ALT may indicate liver stress or inflammation caused by one of the following:

• Viral hepatitis
• Non-alcoholic fatty liver disease (NAFLD)
• Alcohol-related liver concerns
• Autoimmune hepatitis
• Cirrhosis (scarring of the liver)
• Liver ischemia (reduced blood flow to the liver)
• Liver cancer
• Hemochromatosis (iron overload)
• Wilson's disease (copper overload)
• Mononucleosis (caused by Epstein-Barr virus)
• Drug-induced liver stress can be caused by acetaminophen, amiodarone, antibiotics, fluconazole, methotrexate, nonsteroidal anti-inflammatory drugs (NSAIDs), phenytoin, statin medications, tricyclic antidepressants, valproate, vitamin A

Extrahepatic causes of elevated ALT include:

• Heart disease
• Kidney disease
• Muscle injury and exercise
• Celiac disease
• Thyroid disorders
• Dyslipidemia
• High blood sugar and diabetes 
• Obesity
• Hemolysis (destruction of red blood cells)

Symptoms Associated With High ALT Levels

Sometimes, patients don't have any symptoms associated with high ALT levels. If ALT levels are high due to liver concerns, they may report:

• Abdominal pain and swelling
• Jaundice (a yellowing of the skin and eyes)
• Nausea and vomiting
• Itching 
• Fatigue
• Loss of appetite
• Pale stools
• Dark urine (1, 42) 

Patients with any new or worsening symptoms should seek medical care for evaluation. Additionally, patients with elevated ALT levels on bloodwork should follow up with their healthcare provider to determine the underlying cause of the elevation of the liver enzyme. 

Routine follow-up is also important for patients diagnosed with liver conditions to monitor progression, assess the effectiveness of management strategies, and address any complications.

Lab Tests and Diagnostic Procedures for High ALT Levels

A healthcare professional may order ALT to screen for, monitor, or evaluate liver conditions. For screening purposes, ALT is usually ordered alongside AST. If ALT and/or AST come back elevated, a more comprehensive liver function panel may be ordered with the following components to confirm liver chemistry is abnormal:

• ALT
• AST
• ALP
• Gamma-glutamyltransferase (GGT)
• Bilirubin
• Albumin

Liver transaminase elevations are classified as:

• Mild: < 5 times the upper reference limit 
• Moderate: 5-10 times the upper reference limit
• Marked: > 10 times the upper reference limit

Specific patterns in liver function tests can help guide the evaluation:

A comprehensive medical history and physical examination should be conducted during the preliminary workup of elevated ALT levels. This should include: 

• Family history of liver conditions
• Medication and supplement recall
• Drug and alcohol use
• Risk factors for viral hepatitis and NAFLD
• Signs and symptoms of liver concerns 

Marked or persistent mild-to-moderate elevations of ALT warrant additional diagnostic testing, which may include: 

• Complete blood count (CBC) with platelets
• Prothrombin time
• Viral hepatitis panel
• Autoimmune hepatitis panel 
• Ceruloplasmin
• Iron panel 
• Epstein-Barr virus panel
• Hemoglobin A1c
• Lipid panel
• Thyroid panel
• Celiac antibodies 

Liver ultrasound is a non-invasive and inexpensive imaging technique that can help evaluate certain liver conditions by revealing fatty deposits, inflammation, scarring, or other lesions in the liver. Your doctor may recommend additional testing or imaging to follow up on and confirm ultrasound results. These are typically ordered/performed by a liver specialist and may include: 

• Liver biopsy: a small sample of liver tissue is removed, usually with a needle, for microscopic examination
• Computed tomography (CT): X-rays and computer processing create detailed cross-sectional images of the liver
• Magnetic resonance imaging (MRI): magnetic fields and radio waves are used to produce detailed images of the liver and surrounding structures
• Magnetic resonance elastography: uses MRI to measure the stiffness of liver tissue, providing a non-invasive assessment of liver fibrosis and progression. 
• FibroScan: transient elastography measures liver stiffness, helping to assess the degree of liver fibrosis without needing a traditional biopsy.

Managing and Supporting Healthy ALT Levels

The management of high ALT levels varies depending on the underlying factors. Patients with liver concerns should receive specialized care from a hepatologist and adhere to recommended management strategies. Adjunctive care, such as lifestyle and dietary modifications, can support overall liver health. These recommendations are also beneficial for individuals seeking to support liver health proactively and maintain healthy liver enzyme levels.

Dietary Changes

Eating a healthier diet, such as the Mediterranean diet, can help support liver health and maintain healthy ALT levels: 

• Limit dietary sugar intake to less than 3% of total daily caloric intake
• Reduce saturated fats to less than 10% of total fat intake
• Eliminate trans fats from the diet
• Incorporate polyunsaturated fatty acids (PUFAs), especially omega-3 fatty acids, into the diet by eating fatty fish, walnuts, flaxseeds, sunflower seeds, and tofu. 
• Eat more nuts; more frequent nut consumption has been associated with a lower prevalence of NAFLD.

Heavy drinking is associated with an increased risk of liver concerns. Sustaining from alcohol consumption is recommended to support healthy liver enzyme levels. When you drink, drink alcohol in moderation. This means drinking no more than two alcoholic beverages daily for men and no more than one drink daily for women. 

Several studies have found that drinking one to four cups of coffee daily can help support healthy ALT levels and promote liver health. 

Because folate deficiency has been linked to higher ALT and GGT levels, consider adding more folate-rich foods into your diet, including: 

• Beef liver
• Asparagus
• Leafy green vegetables
• Brussels sprouts
• Avocado
• Beans
• Fortified grains

Exercise

Significant reductions in ALT levels have been observed in patients who adhere to resistance and aerobic exercise protocols, particularly those lasting at least 12 weeks. Exercise enhances insulin sensitivity, aids in managing cholesterol and blood sugar levels, and supports a healthy weight, all of which contribute to optimal liver health. 

Supplements

Silymarin is the antioxidant and anti-inflammatory constituent isolated from milk thistle, an herb renowned for its liver-supportive properties. Studies suggest the use of silymarin supplements as a complementary approach in various liver health strategies. Doses ranging from 80 to 2,100 mg daily for 28 days to 48 weeks have been found effective in supporting healthy ALT levels. 

A 2017 study found that 1 mg of folic acid daily for one month was just as effective as 5 mg/kg of silymarin daily in supporting healthy liver enzyme levels in children with epilepsy and drug-induced liver stress.

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Key Takeaways

• High ALT levels can indicate liver inflammation or stress, necessitating further evaluation and management. 
• Proactive measures, such as maintaining a healthy diet, exercising regularly, and avoiding excessive alcohol consumption, can support liver health. 
• Patients diagnosed with elevated ALT should discuss their test results promptly with a healthcare provider to determine the appropriate next steps and underlying causes. Seeking medical advice for persistent symptoms or concerns about liver function ensures early detection and intervention for liver issues.