Alanine Aminotransferase (ALT)
Alanine aminotransferase is a cytosolic transaminase enzyme localized primarily within hepatocytes. It is the most specific circulating biomarker for acute or chronic hepatocellular injury.
Standard vs. Optimal Reference RangesU/L
Standard reference intervals represent the statistical 95% distribution of unselected commercial populations. Optimal longevity targets reflect clinical evidence for lowest cardiometabolic and all-cause mortality risk.
Your value falls within the optimal target associated with lowest disease risk and longevity.
7 - 56 U/L (Commercial lab ceiling often up to 50 U/L)
General reference distribution across unselected commercial populations.
12 - 25 U/L (Male: < 30 U/L, Female: < 20 U/L)
Concentration target associated with minimal all-cause cardiometabolic mortality.
Molecular Mechanism & Clinical Purpose
ALT catalyzes the reversible transfer of an amino group from L-alanine to alpha-ketoglutarate, producing pyruvate and L-glutamate for the tricarboxylic acid (TCA) cycle. Hepatocyte plasma membrane damage releases cytosolic ALT into the systemic circulation.
Differential Diagnosis
Elevated Levels (ALT High)
- •Metabolic dysfunction-associated steatohepatitis (MASH / NAFLD)
- •Viral hepatitis (A, B, C)
- •Alcohol-related liver disease
- •Drug-induced liver injury (Acetaminophen, statins, NSAIDs)
Low Levels (ALT Low)
- •Optimal hepatic parenchymal integrity
- •Vitamin B6 (Pyridoxal-5-phosphate) deficiency (co-factor for ALT assay)
Technical Reference & Deep Dive
Biochemistry & Enzymatic Pathways
Longevity Risk Architecture & Epidemiology
Pre-Analytical Caveats & Diagnostic Workup
Pre-Analytical Considerations:
A 12-hour overnight fast is recommended, especially if assessing biliary markers or lipid-associated hepatic enzymes. Complete abstinence from ethanol for at least 48 to 72 hours prior to testing is mandatory to prevent enzyme induction. Avoid strenuous unaccustomed weightlifting for 48 hours prior, which can release muscular transaminases and elevate AST/ALT.
Reflexive Testing Protocol:
- Comprehensive Hepatic Viral Panel (Hepatitis A IgM, HBsAg, HBcAb, HCV antibody with reflex PCR)
- Vibration-Controlled Transient Elastography (FibroScan) or Magnetic Resonance Elastography to quantify hepatic fat and fibrosis
- Serum Ferritin and Total Iron-Binding Capacity (TIBC) to screen for hereditary hemochromatosis
- Autoimmune Liver Disease Serology (Anti-Nuclear Antibodies, Anti-Smooth Muscle Antibodies, Anti-Mitochondrial Antibodies)
- Abdominal Right Upper Quadrant Ultrasound to assess hepatic parenchyma, biliary ducts, and portal vein flow
Clinical Citations & Primary Literature (1)
- [1]Re-evaluating Normal Alanine Aminotransferase Cutoffs in Clinical Practice - Hepatology (2021). PMID: 33894012
Associated Longevity Guides & Clinical Calculators
Medicine 3.0Explore comprehensive evidence-based clinical protocols, testing costs, and algorithmic calculators that incorporate Alanine Aminotransferase (ALT) into overall healthspan optimization.