According to the Mexican Radiation Safety regulations for patients treated in a nuclear medicine service, the exposure rate limit at 1 m from the patients is 5 mR/h before leaving the hospital. Three groups of patients have been monitored after: a) whole body bone studies with 740 MBq of 99mTc‐MDP (207 patients); b) infection studies after i.v. administration of 185 MBq of 67Ga (207 patients); and c) thyroid studies with 185 MBq of 131I (142 patients). The results indicated that the average exposure rate levels in each group were: a) 0.57 ± 0.17 mR/h, b) 0.47 ± 0.20 mR/h, and c) 0.86 ± 0.14 mR/h. This study has shown that the Nuclear Medicine Department at INCAN complies with the NOM‐013‐NUCL‐1995 Mexican regulation.