The demand for high value health care uncovered a steady trend in laboratory tests ordering and inappropriate testing practices. Residents' training in laboratory ordering practice provides an opportunity for quality improvement. We collected information on demographics, the main reason for the appointment, preexisting medical conditions and presence of co-morbidities from first-visit patients to the internal medicine outpatient service of our university general hospital. We also collected information on all laboratory tests ordered by the attending medical residents. At a follow-up visit, we recorded residents' subjective perception on the usefulness of each ordered laboratory test for the purposes of diagnosis, prognosis, treatment or screening. We observed that 17.3% of all ordered tests had no perceived utility by the attending resident. Tests were usually ordered to exclude differential diagnoses (26.7%) and to help prognosis estimation (19.1%). Age and co-morbidity influenced the chosen category to legitimate usefulness of tests ordering. This study suggests that clinical objectives (diagnosis, prognosis, treatment or prevention) as well as personalization to age and previous health conditions should be considered before test ordering to allow a more appropriate laboratory tests ordering, but further studies are necessary to examine this framework beyond this medical training scenario.