What's the normal level of serum creatinine?

Any < 1.5 mg/dL. : The standard reference ranges for serum creatinine are 0.5 to 1.0 mg/dl (about 45-90 μmol/l) for women and 0.7 to 1.2 mg/dl (60-110 μmol/l) for men. These can vary. For example, a bodybuilder can have a creatinine level of 2.0 and be healthy, while an elderly female can have a value of 1.2 and have severe renal disease.

S. Creatinine: 0.6-1.3 mg./DL in adult males, and 0.5-1.1 in adult females.