In the United States and in most European countries creatinine is usually reported in mg/dL, whereas in Canada, Australia, and a few European countries, μmol/L is the usual unit. One mg/dL of creatinine is 88.4 μmol/L.
The typical human reference ranges for serum creatinine are 0.5 mg/dL to 1.0 mg/dL (about 45 μmol/L to 90 μmol/L) for women and 0.7 mg/dL to 1.2 mg/dL (60 μmol/L to 110 μmol/L) for men. The significance of a single creatinine value must be interpreted in light of the patient's muscle mass.  Patients with greater muscle mass have higher creatinine concentrations.
The trend of serum creatinine concentrations over time is more important than absolute creatinine concentration.
Serum creatinine concentrations may increase when an ACE inhibitor (ACEI) is taken for heart failure and chronic kidney disease. ACE inhibitors provide survival benefits for patients with heart failure and slow the disease progression in patients with chronic kidney disease. An increase not exceeding 30% is to be expected with ACEI use. Therefore, usage of ACEI should not be stopped unless an increase of serum creatinine exceeded 30% or hyperkalemia develops.