They really depends upon labs, age, gender etc but
the following are geneally cited

adult male: 40-160 mg/dL or 0.45-1.81 mmol/dL.
adult female: 35-135 mg/dL or 0.42-1.52 mmol/dL.

I believe Zhang Gongyao's 2.5 multiple is
2.5 mutlptle of upper limit and is crteria
for potential clinically significant abnormalities