What are the normal reference ranges for serum glutamic‑oxaloacetic transaminase (AST, SGOT) and serum glutamic‑pyruvic transaminase (ALT, SGPT)?

Normal SGOT (AST) and SGPT (ALT) Values

The normal reference ranges for AST (SGOT) are 11-34 U/L for both genders, and for ALT (SGPT) are 8-41 U/L for females and 9-59 U/L for males, based on standardized IFCC methods. 1

Standard Laboratory Reference Ranges

The most widely accepted reference intervals from standardized multicenter studies are:

• AST (SGOT): 11-34 U/L (0.18-0.57 μkat/L) - no gender partitioning required 1
• ALT (SGPT) for females: 8-41 U/L (0.13-0.68 μkat/L) 1
• ALT (SGPT) for males: 9-59 U/L (0.15-0.99 μkat/L) 1

These values were established through IFCC-standardized reference measurement systems across multiple international centers, examining 765 carefully selected healthy individuals aged 18-85 years. 1

Updated Lower Thresholds for Liver Disease Detection

More stringent upper limits have been proposed to improve sensitivity for detecting early liver disease:

• ALT for males: 30 U/L (500 nkat/L) 2
• ALT for females: 19 U/L (317 nkat/L) 2

These lower thresholds demonstrate superior sensitivity (76.3% vs 55%) for identifying patients with hepatitis C viremia while maintaining acceptable specificity (88.5% vs 97.4%). 2 The increased sensitivity particularly targets patients with minimal to mild histologic liver lesions. 2

Contemporary Asian Population Data

Recent metabolically and histologically verified data from Asian living liver donors suggest even lower upper reference limits:

• ALT for males: 34 U/L 3
• ALT for females: 22 U/L 3

Using these thresholds, 72.8% of males with ALT ≥34 U/L and 55% of females with ALT ≥22 U/L showed hepatic steatosis. 3

Clinical Context-Specific Ranges

NAFLD/NASH Populations

In patients with nonalcoholic fatty liver disease, ALT values typically range from low normal to 250 U/L, usually less than 5× upper limit of normal (ULN). 4 AST values are typically lower than ALT, though with advanced fibrosis AST may exceed ALT. 4 Most central laboratories use ULN for ALT around 40-45 U/L. 4

Gender-Specific Considerations

The American College of Gastroenterology considers true normal ALT levels to range from 29-33 U/L for males and 19-25 U/L for females. 5 The American Association of Clinical Endocrinology recommends ALT upper limits of 30 U/L for men and 19 U/L for women. 5

Important Clinical Caveats

Laboratory variation exists: ULN values for ALT and AST may vary between laboratories from less than 30 U/L to more than 70 U/L due to differences in reference populations and analytical methods. 4 6

Normal values don't exclude disease: Patients with NAFLD and normal aminotransferase levels can still have significant steatohepatitis and develop advanced fibrosis or cryptogenic cirrhosis. 5 Up to 50% of patients with type 2 diabetes have NAFLD despite ALT levels <40 U/L. 5

AST specificity: While both aminotransferases are concentrated in the liver, AST elevations can occur from disorders involving heart, skeletal muscle, kidneys, brain, and red blood cells, whereas ALT elevations are more specific for liver injury. 6