Pre-analytical preparation of the patient is extremely important in laboratory tests because of the great influence on their final results. In order to avoid errors in the pre-analytical phase, it is necessary to emphasize the importance of general instructions for preparation for laboratory tests and to instruct patients to perform proper preparation before taking the sample. In the pre-analytical phase of the laboratory process, 46 to 68% of all laboratory errors occur, most often due to lack of information about proper preparation before sampling and handling of samples. The paper sought to identify where the error most often occurs, whether there is sufficient education of staff in primary care and nurses in primary care on patient preparation, and whether there is a problem of neglect of primary care instructions by patients. The paper presents a prospective, survey research. Data collected by an anonymous survey at the Department of Medical Biochemical Activity of the General Hospital Pula in August 2020 were analyzed. The MedCalc R statistical program and the software version of Excell 2016 were used to process the results. The obtained results were presented as a mean and a percentage. The questionnaire from Appendix 1, which contained 11 questions, was filled in with the help of an examiner. The group of 100 patients consisted of 72 women (72%) with a mean age of 46 years and 28 men (28%) with a mean age of 57 years of different levels of education. Insufficient education of patients with the need for further clarification of basic instructions for preparation for blood sampling and collection of morning urine. It was determined that the staff in primary health care is not sufficiently educated in the form of preparation for laboratory tests and it is necessary to improve education and communication in the field of laboratory diagnostics.