What are the reference ranges for AST and ALT?

• A. AST 5-35 U/L; ALT 7-45 U/L
• B. AST 10-40 U/L; ALT 8-50 U/L
• C. AST 0-20 U/L; ALT 0-25 U/L
• D. AST 20-60 U/L; ALT 15-60 U/L

Answer: (A)

Normal reference ranges set the values seen in a healthy person and are used to interpret test results. For AST and ALT, adult reference ranges are typically in the range of about 5–40 U/L for AST and 7–45 U/L for ALT. The option showing AST 5–35 U/L and ALT 7–45 U/L aligns with these common values, making it the best match among the choices. Other options present ranges that are either implausibly low (zero lower limit) or have upper limits that don’t fit what many laboratories use in practice. Remember, exact numbers can vary slightly by lab, but this combination sits closest to standard reference values.