Creatinine adjustment has been used to remove the influence of the effect of urine dilution on exposure biomarkers measured in spot samples. This research aimed to determine the reliability of creatinine adjustment for urinary chromium and arsenic in subjects from general population considering interferences able to influence creatinine excretion. 444 male subjects were examined and each participant was administered an anamnestic questionnaire. Chromium and arsenic were determined on second morning void urine samples by atomic absorption spectrophotometry and creatinine by Jaffè method. Urinary creatinine showed a significant negative decrease with age increasing (p < 0.001). Chromium concentrations resulted higher in subjects with renal disease, particularly after creatinine adjustment (p = 0.014). Age was negatively correlated with urinary creatinine (rho = -0.23; p < 0.001), and positively with chromium (rho = 0.13; p = 0.007) and arsenic (rho = 0.17; p = 0.004), only after creatinine adjustment. A positive correlation was also found between unadjusted chromium and arsenic (rho = 0.10; p = 0.039) and between urinary creatinine and both unadjusted chromium (rho = 0.32; p < 0.001) and arsenic (rho = 0.18; p < 0.001). An high coefficient of correlation was observed between unadjusted chromium (rho = 0.88; p < 0.001) and arsenic (rho = 0.90; p < 0.001) and the respective adjusted values. Multiple regression showed a dependence of urinary creatinine and adjusted chromium and arsenic concentrations on age. In conclusion, although chromium and arsenic seem to have a renal kinetics of excretion comparable to the creatinine one, the influence of age on creatinine elimination suggests that the expression of urinary values of these metallic elements as microg/L is more reliable.