Errors in the clinical laboratory are very frequent, most of which are mostly during the pre-analytical phase. That is why this research work proposes the identification of pre-analytical errors in the external office area of the Dos de Mayo National Hospital. To do this, a form was applied, filled out by the researcher at the time of supervision of the sampling. The instrument was validated by the joint recommendations of the EFLM-COLABIOCLI (European Federation of Clinical Chemistry and Laboratory Medicine) and the Latin American Working Group of the Pre-Analytical Phase (WG-PRE-LATAM) of the Latin American Confederation of Clinical Biochemistry. It was obtained as a result, among the most outstanding, that more than 90% of the patient was not recommended to rest for 5 minutes at the end of the phlebotomy, 80% did not register the identity of the phlebotomist in the request for examina...