What are the reference ranges for total CK for men and women respectively?

• A. Male 15-160 U/L; Female 15-130 U/L
• B. Male 10-150 U/L; Female 10-140 U/L
• C. Male 20-180 U/L; Female 20-130 U/L
• D. Male 5-100 U/L; Female 5-90 U/L

Answer: (A)

The concept being tested is that total CK reference values differ by sex because men typically have more skeletal muscle mass, leading to a higher upper limit in healthy individuals. A common, lab-standard pairing is a similar lower limit for both sexes (around 15 U/L) but a higher upper limit for men (about 160 U/L) and a slightly lower one for women (about 130 U/L). The option with male 15-160 U/L and female 15-130 U/L matches this pattern and aligns with many clinical lab references. Other ranges often start at a much lower minimum or set upper limits that don’t reflect the sex-based difference in CK levels, making them less consistent with standard practice. Keep in mind that exact numbers can vary by assay and lab, but the principle of higher upper limits in men due to greater muscle mass remains constant.