Medication error is one of the public health problems, as many of them can affect patient’s health and lead to increased treatment costs. These errors compromise patient’s level of trust in the healthcare system. The pharmacist must be involved in the process of improving the patient's quality of life by cooperating with the patient and other health professionals. Thus, we aimed to identify the frequency and type of prescription errors in the national health system and their description based on the evidence accumulated from the collected prescriptions. The research methods were determined by the information collected based on the analysed prescriptions, direct interviews, brainstorming method and voluntary reports. The research batch included 754 prescriptions with 1104 drugs, with an average of 1.46 ± 0.66 drugs per prescription. In the 754 prescriptions analysed, 1872 errors were detected, the most frequent being: errors in the name of medicines (22.54% CI95: 19.5575-25.5225), errors in the pharmaceutical form (16.97% CI95: 14.2907-19.6493), lack of information about the patient (10.74% CI95: 8.5300-12.9500), lack of information about the doctor (90.18% CI95: 87.8780-92.4820) and errors in the period of validity of the prescription (87.93% CI95: 85.6046-90.2554). The identification and analysis of the errors will allow the development of the strategies of improvement for the health care systems safety. Taking into account that it is not possible to prevent all the errors, and in order to act before they reach the patient, it is necessary to implement controls in the working procedures that allow the detection of errors.