What does low AST mean?
Low AST levels (below 10 U/L) are generally not concerning and may indicate good liver health, though extremely low levels could suggest vitamin B6 deficiency or reduced muscle mass. Most doctors focus on elevated AST levels, which signal liver damage or other health issues.
Understanding AST and Its Role in Your Body
Aspartate aminotransferase (AST) is an enzyme found primarily in your liver, but also in your heart, muscles, kidneys, brain, and red blood cells. This enzyme plays a crucial role in amino acid metabolism, helping your body process proteins and convert them into energy. When cells in these organs are damaged, AST is released into your bloodstream, which is why doctors use AST levels as a marker for organ health, particularly liver function.
AST testing is typically part of a comprehensive metabolic panel or liver function test. While most medical attention focuses on elevated AST levels, which can indicate liver damage, heart problems, or muscle injury, some people discover they have low AST levels and wonder what this means for their health.
What Are Normal AST Levels?
Normal AST levels typically range from 10 to 40 units per liter (U/L) for adults, though this can vary slightly between laboratories and may differ based on factors like age and sex. Generally, men tend to have slightly higher AST levels than women. Children may have higher normal ranges, particularly during growth spurts.
AST Levels and Clinical Significance
| AST Level (U/L) | Category | Clinical Significance | Common Causes | |
|---|---|---|---|---|
| Below 10 | <10 U/L | Low | Usually benign, may need B6 evaluation | Vitamin B6 deficiency, kidney disease, pregnancy |
| 10-40 | 10-40 U/L | Normal | Healthy liver function | Normal variation |
| 41-120 | 41-120 U/L | Mildly Elevated | Possible liver inflammation | Fatty liver, medication effects, alcohol use |
| Above 120 | >120 U/L | Significantly Elevated | Liver damage likely | Hepatitis, cirrhosis, liver injury |
AST levels should always be interpreted alongside ALT and other liver function markers for accurate diagnosis.
Low AST is generally defined as levels below 10 U/L, though some laboratories may use slightly different cutoff points. It's important to note that AST levels can fluctuate throughout the day and may be influenced by recent physical activity, as exercise can temporarily increase AST levels due to muscle exertion.
Understanding your AST levels in context with other liver enzymes and biomarkers provides a more complete picture of your liver health.
Common Causes of Low AST Levels
Vitamin B6 Deficiency
The most common cause of low AST levels is vitamin B6 (pyridoxine) deficiency. AST requires vitamin B6 as a cofactor to function properly, so when B6 levels are low, AST activity decreases. This deficiency can occur due to poor dietary intake, malabsorption disorders, certain medications (like isoniazid for tuberculosis), or increased needs during pregnancy.
Chronic Kidney Disease
Patients with chronic kidney disease, particularly those on hemodialysis, often have low AST levels. This occurs because dialysis can remove vitamin B6 from the blood, and kidney disease can affect the body's ability to maintain proper enzyme levels. Regular monitoring of liver enzymes is important for kidney disease patients.
Other Potential Causes
- Pregnancy (due to increased vitamin B6 requirements)
- Certain medications that interfere with vitamin B6 metabolism
- Severe malnutrition
- Genetic variations affecting enzyme production
- Advanced age (enzyme levels may naturally decline)
- Autoimmune conditions affecting enzyme production
Symptoms Associated with Low AST
Low AST levels themselves don't typically cause symptoms. Instead, any symptoms you experience are likely related to the underlying cause of the low AST. For example, if vitamin B6 deficiency is the cause, you might experience:
- Skin rashes or dermatitis
- Cracks or sores around the mouth
- Swollen, smooth tongue
- Mood changes, including depression or confusion
- Weakened immune function
- Anemia symptoms (fatigue, weakness, pale skin)
- Peripheral neuropathy (tingling in hands and feet)
If chronic kidney disease is the underlying cause, symptoms might include fatigue, swelling, changes in urination patterns, and high blood pressure. It's important to work with your healthcare provider to identify and address the root cause rather than focusing solely on the AST level itself.
Upload your blood test results to track your progress
Seamlessly upload 3rd party biomarker & blood tests to track your whole health in 1 dashboard. Understand what each blood test means and how it fits into the bigger picture of your body and health.
Get diet and lifestyle recommendations based on your blood results, health profile and health goals. You'll also receive a custom supplement recommendation for the precise nutrients your body craves.
Upload Past Blood Test Results
Click or drag file to upload
Once you upload your report, we'll extract the results for your review. Works with top labs including Quest Diagnostics, LabCorp, BioReference, EverlyWell, LetsGetChecked and hundreds of other labs.
When to Be Concerned About Low AST
In most cases, low AST levels are not a cause for concern and may even indicate that your liver and other organs are functioning well without cellular damage. However, you should consult with your healthcare provider if:
- Your AST levels are consistently below 5 U/L
- You have symptoms of vitamin B6 deficiency
- You have known kidney disease or are on dialysis
- You're taking medications that may affect vitamin B6 levels
- You have other abnormal liver function test results
- You're experiencing unexplained fatigue or other concerning symptoms
Your doctor may recommend additional testing to evaluate vitamin B6 levels, kidney function, or other potential causes. They might also review your medications and dietary habits to identify factors contributing to low AST levels.
Testing and Monitoring Your AST Levels
AST testing is typically done as part of a comprehensive metabolic panel or liver function test. The test requires a simple blood draw and usually doesn't require fasting, though your doctor may give you specific instructions based on what other tests are being performed simultaneously.
For a complete picture of your liver health, AST is usually tested alongside other enzymes and markers including ALT (alanine aminotransferase), alkaline phosphatase, bilirubin, and albumin. The ratio of AST to ALT can provide additional diagnostic information about the type and severity of liver conditions. Regular monitoring of these biomarkers can help you track your liver health over time and catch potential issues early.
Interpreting Your Results
When reviewing your AST results, remember that:
- A single low reading may not be significant
- Results should be interpreted in context with other liver function tests
- Recent exercise or physical activity can affect results
- Different laboratories may have slightly different reference ranges
- Age, sex, and muscle mass can influence normal values
Treatment and Management Strategies
Addressing Vitamin B6 Deficiency
If low AST is due to vitamin B6 deficiency, treatment typically involves:
- Dietary changes to include more B6-rich foods (poultry, fish, potatoes, chickpeas, bananas)
- Vitamin B6 supplements (typically 1.3-1.7 mg daily for adults)
- Addressing underlying malabsorption issues if present
- Adjusting medications that may interfere with B6 metabolism
Managing Underlying Conditions
For low AST related to chronic conditions:
- Kidney disease patients may need B6 supplementation, especially if on dialysis
- Regular monitoring of nutritional status
- Working with a nephrologist or specialist to optimize treatment
- Ensuring adequate protein intake while managing kidney function
The Bigger Picture: AST and Overall Health
While low AST levels are generally not harmful, they serve as a reminder of the interconnected nature of our body's systems. AST is just one piece of the puzzle when it comes to understanding your metabolic and liver health. Comprehensive testing that includes multiple liver enzymes, metabolic markers, and nutritional indicators provides a more complete picture of your health status.
Regular health monitoring can help you identify trends and catch potential issues before they become serious problems. This is particularly important if you have risk factors for liver disease, kidney problems, or nutritional deficiencies. By staying proactive about your health and working with healthcare providers who understand the nuances of biomarker interpretation, you can maintain optimal health and address any concerns before they escalate.
Moving Forward with Low AST Levels
If you've discovered you have low AST levels, don't panic. In most cases, this finding is benign and may even indicate good organ health. However, it's worth investigating further if your levels are extremely low or if you have symptoms suggesting vitamin B6 deficiency or other underlying conditions. Work with your healthcare provider to determine if additional testing is needed and whether any dietary or lifestyle changes would be beneficial.
Remember that optimal health involves more than just normal lab values. Focus on maintaining a balanced diet rich in essential nutrients, staying physically active, managing stress, and getting regular health checkups. By taking a comprehensive approach to your health, you can ensure that all your body's systems, including those that produce and regulate enzymes like AST, function at their best.
References
- Sookoian S, Pirola CJ. Liver enzymes, metabolomics and genome-wide association studies: from systems biology to the personalized medicine. World J Gastroenterol. 2015;21(3):711-725.[PubMed][DOI]
- Lumeng L, Li TK. Vitamin B6 metabolism in chronic alcohol abuse. Pyridoxal phosphate levels in plasma and the effects of acetaldehyde on pyridoxal phosphate synthesis and degradation in human erythrocytes. J Clin Invest. 1974;53(3):693-704.[PubMed]
- Okada M, Shibuya M, Yamamoto E, Murakami Y. Effect of diabetes on vitamin B6 requirement in experimental animals. Diabetes Obes Metab. 1999;1(4):221-225.[PubMed]
- Giannini EG, Testa R, Savarino V. Liver enzyme alteration: a guide for clinicians. CMAJ. 2005;172(3):367-379.[PubMed][DOI]
- Kwo PY, Cohen SM, Lim JK. ACG Clinical Guideline: Evaluation of Abnormal Liver Chemistries. Am J Gastroenterol. 2017;112(1):18-35.[PubMed][DOI]
Was this article helpful?
Frequently Asked Questions
How can I test my AST at home?
Is low AST dangerous?
What foods can help increase AST levels?
How often should I test my liver enzymes?
Can exercise affect AST levels?
This article is licensed under CC BY 4.0. You are free to share and adapt this material with attribution.
