Understanding ALT 32 with Normal AST
An ALT of 32 U/L with normal AST is within normal limits for most adults and does not indicate liver injury. This pattern requires no intervention unless other clinical factors suggest liver disease.
Normal Reference Ranges and Clinical Context
Normal ALT levels are 29-33 IU/L in men and 19-25 IU/L in women, making an ALT of 32 U/L at the upper end of normal for men and mildly elevated for women 1.
ALT is the most liver-specific enzyme because it has minimal presence in cardiac muscle, skeletal muscle, kidneys, and red blood cells, unlike AST which is found in all these tissues 1, 2, 3.
AST is less specific for liver injury and can be elevated in cardiac disorders, skeletal muscle injury from exercise, kidney disease, and red blood cell disorders 1.
Clinical Significance of This Pattern
An AST/ALT ratio <1 (normal AST with ALT at 32) is the typical pattern seen in early or mild hepatocellular conditions like nonalcoholic fatty liver disease (NAFLD), viral hepatitis, or medication-induced liver injury 1.
However, ALT of 32 U/L does not meet criteria for hepatocellular injury, which requires ALT ≥5× upper limit of normal (≥165 U/L for men, ≥125 U/L for women) to warrant close observation 4.
This level does not trigger any monitoring algorithms outlined in consensus guidelines for drug-induced liver injury or chronic liver disease 4.
When to Consider Further Evaluation
If the patient is female, an ALT of 32 U/L represents mild elevation (upper limit 25 IU/L), which may warrant repeat testing in 2-4 weeks if there are risk factors for liver disease 1.
Assess for metabolic syndrome components (obesity, diabetes, hypertension) as risk factors for NAFLD, detailed alcohol consumption history, and complete medication review including over-the-counter drugs and supplements 1.
Repeat liver enzymes in 2-4 weeks only if clinical suspicion exists based on symptoms (fatigue, jaundice, pruritus, right upper quadrant pain) or risk factors 1.
Important Clinical Pitfalls
Do not assume normal ALT completely excludes liver disease, as some patients with significant liver pathology may have normal ALT levels, particularly in chronic hepatitis C where ALT can be normal despite active disease 2, 5.
AST may remain elevated when ALT is normal in certain conditions, suggesting that measuring both enzymes provides complementary information 5.
An AST/ALT ratio ≥1 typically indicates more advanced liver disease (alcoholic liver disease or cirrhosis), but when both are normal or near-normal, this ratio has limited clinical significance 6, 7.